My collection is relatively small - I try to not to pick up stuff I don't necessarily need. If anything I'm trying to downsize a bit. However, if you find something on my tradelist you could use, here are my collecting priorities, in rough order:
1) my three primary player collections: Kevin McReynolds, Keith Hernandez, Pete Harnisch. Those are, admittedly, really hard to hit because I've got almost every major release from those guys.
2) autographs from everyone who's played for the Mets. Again, hard to hit because the majority of the guys I need either don't have certified autos, are old/deceased, or both. However, they don't need to be in a Mets uniform, which opens up the pool a bit. My need list: https://docs.google.com/document/d/1qwZl3ADQSf_gVoFHtuS6t3hRaaHnEzRZ3N3h7sJtjkQ
Those are the big two; knowing that those are hard to hit, though and knowing that I just really enjoy trading, here are other things that catch my eye:
3) 1960 Topps. Picked up about 60% of this set from a friend and figured "what the heck, let's go for it." Literally just about any condition as long as there's nothing major (holes, rips) is good for me. I'm down to less than 30 cards for this set, and since they're mostly higher-value cards, I'm really *looking* for off-condition at this point.
4) Mets parallels, but specifically parallels from guys who I really like. :) Mookie Wilson, Ron Darling, Sid Fernandez, Wilmer Flores, and David Wright, mostly, with Nimmo, Gooden, Alonso, and Dom Smith as other options. It's a moving target - sometimes it's just a feel thing. Don't need base, don't need inserts, necessarily, unless they're particularly eye catching.
5) Modern base flagship cards of classic players. The Topps SP variations, basically, of the Clementes and Aarons and Jackie Robinsons and such.
6) Oversized cards. I've always loved the 5x7 parallels of base cards, ever since the mid-80s "Super" sets. They're boxtoppers now, so they're harder to find, and it kind of ties in with #4 a bit, because I really love what Topps has done the last few years with my three favorite sets ever: 1983-1985 Topps.
7) Other G-VG-EX condition vintage. I don't need anything mint. Just love to have some older stuff in my collection. I'm actively looking to downsize a bit, so taking a handful of modern base/low-end inserts off my hands in trade for a few VG/EX vintage is cool by me.
I'm generally pretty easy to trade with, I think, but if you're interested in something valuable or vintage, I'd need something valuable or vintage or off my real wantlists. Thanks for looking!