It's possible to not be in range of their home systems. Make sure to upgrade your transports through the ship design page, landing and re-embarking your forces will apply the updates to those transports for free. The best advice I can give is to obtain Clones, and then spam out clones for the rest of the game. Personally I put my the clone vats on all planets (+4 society), as they train faster than regular troops, significantly faster, which is useful for overwhelming forces. However, it is optimal (when not otherwise in direct need) to produce all your clones from a single planet, one with the military base/any other military based enhancements present on it, and if your species on said planet lacks the strong/very strong trait, I'd recommend investing in the DNA changer for that planet alone, and give them strong/resilient, and focus all future army production from then on out no that planet. Genetic Super Soldiers are the later advancement down the society tree, which allows for the creation of the best soldiers in the galaxy (minus a few Godzillas that ARE in the game, but are so incredibly rare as they are based on an event), but take a very, very long time. If you do produce the Gene Soldiers, do not throw them away, only put them in enemy systems when you are SURE that nothing bad will happen to them (even for me, someone that has an army based governor, empire leader, arms race edict, military training camp, it still takes forever), the cost for the super long production time, they are by far the best troops in the galaxy, capable of repelling or attacking almost any planet. If you intend to go toe to toe with a Fallen Empire you're going to need a shit ton of these, as that's all they use as well. Sheer efficiency wise, for invading, even through fortifications, 12 of these super soldiers would be able to defeat almost any army, through fortifications.
