Wanting to make an Eirika Tactic team

The biggest problem with a setup like this is trying to maintain positioning to allow Seiglinde’s effect to work - they all need to be within 2 spaces of Eirika. For me, the most simple and effective way to buff her is to make her the buffing unit and ally support her with whom you want to buff. Then the ally unit not only bounces back the buffs to Eirika but also passes the ally boost as well.