For building a solar empire you need to use some of your beginning credits to make a capitol ship factory then you need to build a capitol ship(if you don't have enough credits,medal,or crystal just build a missionary ship).After start building your vessels or frigates with the remaining credits,medals,crytals you have. Then send all your ships to settle other planets but if your ships aren't strong enough to attack a enemy then retreat back to one of your planets to make more ships or research something that can do it without sending troops in but i would do that later in the game.Once when you colonize a planet or planets you need to build Extractors and develope living faltilities so you get more credit income.Once when you colonize many planets like that you can research things like vessels,more capital ships,etc...but to do this you need to place research faltities around a planet.After,most other empires will attack your planets so make more ships.That is how I make my empires which conquer all!