I'll quote myself here mainly to save from typing  D):

That's my current mo for Classics - Generations, but that's not set in stone. I've thought about moving towards a more focused version of this, to include only G1 homages. I keep second guessing myself, as I have a lot of fun with the odd figures that are stand alone characters.

Using that statement as a springboard, I have always and always see myself as being a primarily G1 collector. This is the only line I'm a "completionist' with, save for Alternatiors/Binal Tech. With G1, I've limited this habit to US specifically, since the overseas figures are generally expensive. I have a few and want a few, but I have no aim of trying to complete them, nor do I see my collection as "incomplete". I am extremely [humbly] proud and happy to say that I have a complete US G1 collection. It's where I started, and it's the toyline that means the most to me. It has a special-ness that no other toyline has ever had for me. Any other line I've liked, I've liked because it somewhat rekindles that same magic.

From there, the closest thing to ever come close to that is Alternators/Binaltech. One of the things I greatly enjoy about G1 (notably the 84 and much of the 85 cast) is that they're not only real world vehicles, but they're very specific real world vehicles. Mirage, Jazz, Bluestreak, Wheeljack, Smokescreen, Skids . . . each of their alt modes are vehicles that existed in that time period. Alternators took that and ran with it, deliberately homaging G1 in that regard. Note that's not making a RX-8 tricked out with some kind of Martini Racing motif - it's making a RX-8 that exists in the real world into a Transformer character. While the movieverse does this as well, I generally don't care for the unnecessarily complex designs to the robot modes (such as Bumblebee, as I really like the concept Camaro used, I don't care for the robot design). I have a sealed collection of both the Alternators and Binal Tech, and a loose collection of Alternators and the BT variants. Additionally, I felt the need to expand with customs of established characters we didn't get and with characters created on my own or in collaboration with other artists.

That being said, I enjoy loose/complete figures, MIB figures, and sealed figures. I used to be heavily into package design, and much of my appreciation of sealed figures comes from that. The package specimen is end result of all of Hasbro's design process. The loose/complete specimen is the toy's potential. I think a good comparison is fireworks. Unleashed, they can sport a number of cool graphical elements on the package that has an identity of its own; unleashed is an explosion of color that would not be realized otherwise.

Speaking of customs, I do buy multiples of molds I enjoy, typically with some plan in mind. I've came to many days where the lack of available funds forces me into "rainy day" mode. There, I can take a spare figure, and unlock a play pattern that's just not possible with being satisfied with a toy as-is out of the package. While it does allow me to be continually creative and artistic, the aim is having the play pattern akin to model kits.

I enjoy having a cool display, but I also enjoy actually "playing" with my TFs. I've always enjoyed mimicking sounds (such as the revving of cars and sirens) and the famous, classic Transformers sound. Transforming these toys from each mode and back can't be done if it's always on a shelf or behind glass. Sometimes, my displays aren't so "neat" since I'm constantly fidding with things  

 

Thisis what I do: I buy from all the lines, not a completionist, but like to have at least 1 thing from every era. That means that I dont like Beast Machines toys but I do have deluxe jetstorm because I liked the character and that specific toy. I also collect by character meaning that I have almost most main line Bumblebees, Starscreams (need a masterpiece one and a big maybe on Machine Wars one, still dont like it)

 

I've only ever been a completist with MASK toys (complete and done), but I started way too late with Transformers to ever make that a viable proposition.

So with Transformers I focused on collecting everything that looked cool, be they from Beast Wars, Binaltech, Alternators, G1 (US, European AND Japanese), G2, Masterpieces or 'CHUG'.

More recently, I've decided to focus more on just G1 and G2. I'm currently working on an 'exit strategy' for my other Transformers: luckily it's not so much the money that I need, so there's no hurry to be rid of them, but they do take up a lot of room. I'm still no completist, but it's strange to find I am liking more and more G1 and G2 Transformers which in the past looked awful to me (1987 series and later). Sometimes it's the actual blockiness, simplicity and lack of articulation which prove to be the attraction. On the other hand, I am still not at all keen on some G1's (the Seeker jets, the minibots) and the chance that I'll ever want to get those are slim to none.

 

As mentioned by others, I buy what I like. I dont usually have more than 1 copy of a particular Transformers (from a series), unless I am using the other one for a custom. I have nearly 50 Optimus Primes, but each of them is a "different" piece. Its just nice to get what you want and like  

 

If i like it when i see it, and can afford it comfortably, ill buy it. Some figures i buy more for
the alt and some for the robot modes. That said, i do have multiples of the same figure, which i purchased for some reason that made me like it.

 

I buy what I like which is mostly g1, g2, classics, 3rd party, titanuim, animated, prime and mp

I'll buy multiples of a figure even from the same like. I think I have three or more of every dinobot (g1).

 

I'm strictly a G1 collector from seasons 1 and 2 of the cartoon.
I buy mostly MISB reissues and open them and display them in robot mode; only have one of each.
Getting close to having all the ones I want so I'm hoping HasTak releases more!

 

Oh god... let me see...I've been watching this thread for like 2 days, and wanted to have time to reply to it properly.

Here is a breakdown on what I collect in "technical" order of how I collect.

RiD: I have this whole line, well at least everything I want from this line.

Prime: I'm looking for the on screen cast only, at this point. I've already screwed up and got hot shot but, it's all good since I still need Arachnid, Dreadwing, Jet Vehicon, and Breakdown.

WFC/FOC: I'm not sure what I from this line just yet, but there are a few of them I do want like, Bruticus, Shockwave, and Optimus, Soundwave, Soundblaster, and at least the Discs but, we'll see.

I go for Prime/FOC before classics/bw/g1/ect due to availability. Being that I can go to the store and buy them and the others I can't, I put these as "priority" over ones that I have to buy online second hand. I do this mostly because I don't want to have to pay twice as much later on down the road.

Beast Wars: I have most of want I want from this line, I'm really only looking for a few more like, Rattrap (the whole reason why I started collecting in the first place but never got it) Ravage "X9" or whatever his name is, Tigatron, Airrazor, and Terrorsaur.

Movie Line: I've only got 10 left to complete the entire on screen cast. There are 2 or 3 more that I want to put in my classics collection, like Lockdown and Fracture.

Classics: For this, right now I'm going for all the Universe1.0/2.0 ones I missed, I have already got the ones from Generations/RTS that I need now to just pick up the Universe/GDO ones that fit into what I want. I'm not really sure what it is that I want yet, but there are certain figures like, Astrotrain, Prowl, Hound, Silver/Blue Streak, Smoke Screen, Inferno, Optimus, Megs, Jetfire, Powerglide, Silverbolt, ect that I don't have yet, but need/want.

G1: With this line, I'm actually looking for Re-issues/Encore versions instead of the originals. Only exceptions would be if I found them for cheap and then they would only be place holders until I get a fresh/new version. Unfortunately this is the lowest on my list of wants for now. The only reason I don't want the originals, is because to get them in the condition that I want, they are gonna be hella expensive compared to the re-issue.

Cyberverse: I also have a few of the Legions/Legends/Commanders but not a whole lot. Once I get my last shelf, I will finally have a place to put them for once.. lol I'm not a fan of the smaller versions of ones I already have but every now and then I will pick one up since the bigger versions are not out yet... they also look good with Metroplex and the DOTM Arc. Only other "Playset" I want is the Driller.

Others: I do have a few here and there that are from other lines, like a couple BM and a couple of Animated. I do have a few A/E/C figures I wanted but, I will wait until I only have retail figures and G1 left before I go for them.

I have actually put together a "definitive" list of my wants together for the family since they are always telling me, "well I would have bought you a transformer but I don't know which one you wanted". If you want to check it out for some strange reason...here it is. It's not done yet but, you'll get the drift..

3r14nd's Wanted List

 

Alt/BT
Classics/WFC/FOC - These do belong together.
Animated
TFP
MP
Movie leader class and HA (the real one not those crappy little ones)
Optimus Primes