My suggestion is that you should get a good colony cluster lvl 2. If you really want to set up your empire you could explore for two, but that gets pretty long and costly. So if your cheap and lazy like me just start attacking people after the first one. As for a standing army im guessing your talking about a defensively fleet. Thats not bad once you get your clusters and all, I tend to just leave whatevers left over from my attack, sometimes through a couple hundred queens or something as a surprise. but yeah while exploring for planets no reason really to have a standing army, just costs more money. Hope this helps.