Openings leading to open position

king's gambit as white. the best tactical opening. you can throw in the dubious wing gambit against the sicilian (1. e4 c5 2. b4) and many low level players won't know what hit them.

as black, against 1.e4 play the scandinavian. against 1.d4 play the benoni/benko gambit.

I'd suggest as white

1.e4 c5 2.d4 cxd4 3.c3

1.e4 e5 2.d4 cxd4 3.c3

and go for the exchange variation of Caro-Kann, French Defenses.

As black you can try Dragon with Sicilian against e4,

KID or Benko Gambit against d4.

Since you're looking for open positions i'd suggest the following:

1.e4 e6 2.d4 d5 3.exd5 exd5 4.c4 against the french

1.e4 c6 2.d4 d5 3.exd5 cxd5 4.c4 against the caro-kann

Play 2.Nf3 and 3.d4 against the sicilian and you can play lines with this set-up Be3, Qd2, f3, 0-0-0, g4, etc...heading for a kingside attack

Against 1.e5 play the italian game with c3 and d4(instead of the now more common d3) or try the king's gambit

As black play the Tarrasch 1.d4 d5 2.c4 e6 3.Nc3 c5 against d4 and the simply play 1.e5 against e4.

Well, I read in various sources on learning chess that it's better to know general principles of openings and study endgame heavily, probably because you won't be able to use advantage of the better opening if you don't know what to do next, and also because middle- and endgame is playing chess, while opening is mostly memorization.

Thanks for all suggestions guys, I'll have a look at them.