At your current stature, I would say go farm manyus and level your girls, especially the 5* ones. Yes, they will definitely cost you a lot (because they cap out at level 60 unevolved compared to 4* and below which caps out at level 50, and their evolution cost and materials are definitely higher), however having them at higher levels will definitely work well in your favor.

From what I've gathered while lurking around the forums, people will recommend you go either Stage 1-3 or Stage 2-1 to farm manyus.
But what you're really after is the Secret Garden they spawn. As for those two stages, they both spawn the Beginner version of the garden - which will at least guarantee you ONE level 20 manyu.

Affection-wise, you can probably go for the 4-5* girls. Since they have more stats as well (and not to mention affection bonus gets doubled once you evolve them). If not, go for whoever you want XD

Dunno about 2* girls but they've been proven useful... well as sacrifice units when specific event maps require so.

You can look for more info on the beginner's Q and A thread, and the previous event threads as well.

To be honest you have gotten real lucky with your 5* girl rolls, Having one of each type and an extra will serve you well later on, especially stage 12 maps that have a lot of enemies weak to slice damage. One of the best ways to see which girls are worth focusing on is to open the premium gatcha contents tab and compare their max lvl stats. That was how I decided which 3*s to focus my lvls and affection on.

5* and 4* should always be focused before 3* until you have enough that you can't use them all. The stats / special moves and special abilities make them much more important.

I'd say a little levelling via manyus maybe 11-1 and aim for the advanced gardens will cane your stamina mind

Evolving your level 4/5s while expensive pays out

Stack all your best units for your helper squad then switch from team 1 to team 2 as your main squad if you want more balanced teams like you have. Better helper squad the more appealing you look to friends and be able to keep strong friends lets you punch above your own weight.

Check which units have a desirable evolved skill and go for evolving them first and foremost to increase your effective power through passive skills.

Use Affection items on your units you intend to evolve sooner rather than later, affection bonuses double when evolved and evolving reduces a unit's power so high affection can minimize power loss or result in a gain in some stats.

Get rid of the 2* units as soon as possible 2* units don't get a skill when evolved so any exp you're giving the is wasted completely, your 3* units should eventually be replaced, but an evolved 3* still has a skill if you find yourself with not 4*+ to evolve and a 3* with a type advantage can still be more useful than a 4*.

As everyone have been saying, farm some manyus and prioritize leveling your 5* and your 4*s. Eventually, as you gain new girls, you'll swap out your 2* and 3*, so leveling them could be a waste of materials. You can try faming manyus with stage gardens, it's a nice way to gain exp too. Farming for gifts is valuable as well, as long as you keep prioritizing 5* and 4*.
Once again as people already said, evolving 2* seems like a waste, while 3* can be useful. However, I don't evolve anything bellow 4* since my goal is to swap out my remaining 3* as well, so evolving them seems like a waste of gold imho. But whoever you decide to evolve, just don't farm the dragon missions unless you're really about to evolve a girl, and get the girls to level cap before farming lvl 100 dragons if you need them.

Never forget your waifu, regardless the amount of stars she has.

Btw, I noticed the squad set up you posted was your #1 set.
Since your 1st squad will always be your helper squad, you should organize your set #1 by highest power, so your first squad is the most powerful possible, which will help your in-game friends out.

Trying to balance out squads' power and speed is the best way to go for your everyday usage set, but do that on your set #2 (or whatever other number you prefer)