Latvian is not sound opening nor solid. A solid opening for black is caro-kann and french. Tactical players must play gambits.
Why must they play gambits? Tactical players can perfectly well play the French or even Caro-Kann - it shouldn't make a big difference.
Colle System for white (in my opinion this opening is quite solid and there are chances of you getting a strong attack on the kingside) and Caro Kann for black (great endgame chances)