If he's been playing long enough to have event units like Claudia, but still has those lvls, yeah he just needs to use his resources better.

As for combining copies, taking chances past the first guaranteed CR/SU for Gold+ units is just a huge gamble unless you don't mind being a massive whale. It just doesn't have nearly the level of benefit I see most players here railing on about so as a small spender myself, I'm saving mine for eventual rainbow currency for guaranteed premium units.

Learn what you need to farm BSII and get to farming that, then max your core units using the priority lists many here provided. AW as you have the extra crystals and silvers to do so. You have an abundance of good units to choose from, pick the ones that will most easily help you farm the next daily difficulty level or wait until an event to see what you will need most to complete the higher maps so you aren't getting max cost event units.

At a certain point it becomes more efficient to spend your SC on refills to run more maps than continuing to hit Gacha, but you seem to have figured that out now. Consider throwing them at Event maps or Monday daily for more plat armors to hit those high lvls and more gold to pick up the silver fodder needed to fuel your premium units (2k summons).