Hmm, it seems my experience with comics is a little different!
So, right now I sell 11x17 prints (mix of original and fanart), buttons, and comic issues. As a general rule, my comics always sell 3 times as much as my prints. I usually sell 30-60 per issue depending on the con (I have 4 issues out right now) so my print runs are between 150-250. 500 if it's the first book, because those will consistently sell (I go to 3-4 cons in a year though, so those numbers make more sense for me). I'm finding it harder to guess quantities for later issues, so I may actually have some waste with issues 3 & 4. Argh.
As for how many you should ACTUALLY bring, I'd say 75 each, maybe 50 if you don't think it's necessary or you're tight on room (fair warning though--I sold 64 of issue 1 at my first con, so I'm wary of telling you less.). If that con is by chance local, I would market yourself in the area. Print out some flyers to hang in comic shops, colleges, etc. letting them know you'll be at the event. Some cons/venues will even let you hang flyers on site around the convention center. It really helps draw attention to you. I get a noticeable bump in sales if I market ahead of time.
Print wise: Fanart stuff always sells better of course, but it's not a guaranteed sell. Variety is most important. I would only print 15-20 of each (maybe even just 10 if it's original) to test out the design. Some print places, even if it's a high minimum order (like 100), will let you print multiple designs within the order. I would seek those out (I've heard catprint.com is super good). I've only sold out of a print on its first run once, and it was of Sesshomaru--apparently mainstream nostalgia sells well, haha. I printed 20, probably would've sold 25-30 at that con if I had more. Now I print runs of 50 with that one so it lasts me a few cons.
Buttons sell here and there for me, but they're not huge. I've heard of some people whose main money maker are buttons, though. I like having them around, and they're fun to make. Symbols sell best for me since I don't do any fanart with those.
Even aside from merch though, your display is really important too. Having consistent branding and vertical displays will help a lot!