There is no single "best" strategy. Scout around a bit and see what the races around you have to offer and what (if any) threats are imminent. You can steal or trade a lot of techs from the AI, so consentrate on whats really neccessary
Mines gives the best and cheapest early defence against the AI - Point defence are a must - Ship capture can help you steal tech worth a zillion - Combat sensors and training are neccessary when things get serious, but not before - Shields, Armor and a big gun for all non missile combat ships - Ship constructions; you want LC's pretty fast for the large mount (steal it or research it ?) - Troops for capturing planets and keeping your people happy when times are rough - Solar sails for speed - And so on .....