If you're serious about light, you have to get Mike, Mike AW to be precise, so save up 3 eyes if you haven't already.
Also, your light team isn't actually that bad - better than mine when I started throwing mtix at light. With ascension (you kept those UE staffs right?) Sol AW is really good in many situations including rags (unless you're like mvp-racing those 5 min rags, for that you need more than just a good team anyway.) Arty gets buffed (forgot when, too, around December iirc) and while still weaker than Lugh and Iris, is definitely still worth fielding (20 BG refund on burst is no joke, and her buff can be cast on herself + one ally, her nuke dmg cap also gets raised iirc.) Frey may not be meta, but on manual, she brings some insane spike dmg that is actually pretty helpful in early game for AQ and GO and stuff.
Given that you don't have Shingen and there's a UE lull, I would recommend you get Mike, then Lugh, running Herc as soul (if you had Shingen, I would have recommended Iris instead of Lugh.) That's enough for a very potent light team. You don't need every OP light hime to run a good light team. The main issue you'll run into with Lugh is that she's absolutely terrible for AAB, but otherwise you should be able to make her work since you have Sol.
Also, until you get Lugh or Iris, don't write off Tsuku just yet. She may not be anywhere close to meta these days, but she's not a useless unit - that AoE blind is really helpful when those GO with mobs come back for example.