I have no idea what I'm doing

[DGDobrev]

Well, in that case, you are doing something wrong indeed. First of all, why do you need all those peasants? Bowmen are an excellect substitution for them, and they can both burn and slow. The next unit you need is Inquisitors and/or archmagi - you can find some in Shivarius' Tower and the Mage tower in Velarion forest, unless you're really unlucky and got a game without them.

Other useful units are the royal thorns or alchemists - both can spawn in the Marshan Swamp. Also, try to lure the strong unit (usually mages) in front of the horsemen camp in Greenworth away, then go around them, move back in and buy some horsemen or knights (at least one of those is guaranteed to spawn there) and you will be just fine, as they are one the best tanks there is, and for such low level, they alone can make a difference. Another thing you can try is the Dragon's tooth tavern in Arlania - some good units can spawn there as well.

You shoud also reconsider your in-game tactics. If you have a bishop on F1, you don't necessarily put it on A6 straight away, do you? For that matter, if you have a good long-range unit (like inquisitors or bowmen) it doesn't mean you should move it each turn. If you have a good rook on a free line, you should keep it there - for that matter, if you have a good tank that can rule the middle of the battlefield, you should keep him there, as the AI is stupid and usually goes for the units that it can reach. For example, do not be surprised if the AI goes for your archers - this means you simply allowed it to reach them.

Try a party of:

Horsemen, Inquisitors, Bowmen, Priests, Archmagi. If you can't find horsemen, the ancient bears will do.

This party usually rocks the early game, because Horsemen have high initiative and you can move them in the middle of the battlefield straight away. Inquisitors can resurrect any of the lost units, priests can heal the horsemen, the Archmagi can cast magic shield on the horsemen so that they take only 50% damage and use the bowmen to slow/burn anything that is threatening your rear guard.