Playing as black, I think I got myself into a good position, but botched it somehow. Where did I go wrong?

-Well, 16...Ne3 seems like a mistake to me, it opens up his queen, forcing your moves. What about 16...f5 instead? Hmmm... Maybe instead of 15...Qxd4+ you go 15...Qxb2, still applying pressure to the pawn on f4. Your inactive knight and rook in the corner didn't do you much good either. I don't know, I'm just staring at the board here...

I think Tartantyco is right to suspect 16...Ne3, I think 17.Bf2 might cause some serious problems for black there. However I think Qxd4 is okay, it puts your queen on a nice centralized square and weakens white's king. Maybe the move is 16...Nc6 and now Ne3 is threatened.

In a short game I wouldn't have looked further then Bf2 (after 16..Ne3) but black can play Qxd3 which is good! Obviously Qg7 blundering the knight lost the game for you but the rest of the game was nice. I think maybe 5...c6 looks a bit slow though. Trying to castle quickly might have been better. It was also possible to play g5 but likewise I think it takes time.

Thanks for the help guys. I am in the 1050 range right now and this was a "tough match" playing a guy at 1300. Gotta keep working on these things and playing more games!

Rule NR#34

Accept the kings gambit.

Agreed.