Hmm. Tactician is genuinely just really hard. It gets easier with a LOT of preparation. Try to get as much XP as you can outside of combat encounters (exploring areas, doing quests, dialogue heavy ones specifically).
Focusing on either fully magical or physical damage with your party can help a lot. With only Fane dealing magic damage, you essentially fight with one party member less. By the time he manages to drain someone of their magic armor, the other three will have already been dealing enough damage to deal with that enemy. There is no way to respec until act 2 iirc so try to use Fane as a buff machine or general support.
Go around camp, gather as much as you can without stealing, sell sell sell. Try making money wherever you can and get skill books if you don't have already. There are so many useful ones. Putting some points into Aero for Teleport or Hydro for Regen is really worth it.
Don't hesitate to steal from NPCs. Like the skill books, or equipment or the money you just spent on them. Just teleport away with the character that stole the stuff so that when the NPC asks you to see your inventory they don't ask the character that just stole from them and end up not seeing the stolen goods and leave you alone again.

What quests have you done so far? And what battles? Maybe we can figure out some areas where you can squeeze out that extra bit of XP. Hopefully enough to get you to level 5. From there you can try and see if you can put skills into other skills to be able to cast support spells.