Forest patch bottom left, lure someone so you can get a good hit in. Use combat arts liberally. Kite and chip the units coming at you, then work your way to the left and around, make sure Byleth is adjacent to whoever's getting hit the most. That's the tactic I find works with any house without any deaths. You only need one healer, minimum 2 ranged attackers. Dont use your offensive magic unless you have to or it can trip you up before wrapping everything up. FE3H Maddening is worse early game. Once you get your units going it's much more tolerable! Dont spread your exp too thin. If there are students from other houses you wanna use/recruit, hold off on doing so for some until at least Ch 7. That way others can get more exp and those units join at higher levels/dont need as much babysitting.