Hello Arthur,
Welcome to Medieval Age!
It'll help if you can tell us the nation that you're playing as, so that, we can suggest an army composition, taking advantage of the nation's unique unit.
I'm assuming a troop capacity limit of 65 for now.
In any case, in early Medieval Age, you should have success with about 2/3rd to 1/3rd split between infantry and shooters. If you're playing as a nation with unique shooters, maybe about 40 shooters to 25 infantry might help. If you're playing as a nation with unique infantry, maybe about 40 infantry to 25 shooters might help. If you're playing as a nation with unique heavy cavalry, maybe about 5 heavy cavalry and 35 shooters might help.
As for medals, it might help to stay between 200 and 400 medals. You should be able to either find easy bases to attack and return with most of the army intact, or you might find higher age bases with outlying farms and roads. In the latter case, you might lose the entire army, but, you might fill up all your food and gold storage capacity with one or two such attacks.
Feel free to post feedback on how this works out, and we can tweak the army composition to help you better.
Cheers and happy gaming!