Originally Posted by Unregistered

Newbie here.

I have ~148k total power in all 4 units, with ~65k at top, 38k, 25k and 20k.

Do I even have a chance at 3 staring the ultimate levels or should i just let it go and give up? Thanks guys.

My personal recommendation:
First off, hit up the Friends List threads for some strong helper squads. Plenty of good ones around here.
First few days of this next event, spam story maps until 12-3 is unlocked (if it is already, great, if not, blow through maps and don't let 3* OCD slow you down, your priority is getting to 12-3). If you're having issues clearing (not 3*, just clear) the maps, look at the map, put your strong helper squad on the camp that has the shortest route to the boss flag and let them carry you there.
Once you're at 12-3, spam the hell out of it, putting all 5 squads on the top left camp (you're missing out on chests, but they're 2* girls with a low chance of ampy and your priority is leveling, not ampy-maxing) and letting the helper squad burn through the enemies for quick clears, hopefully spawning quite a few SGs. Your stamina will likely be an issue, whether you want to burn FGs on powerleveling vs. gacha yolo pulls is up to you. If you're not using FGs, ALWAYS make sure before you start a 12-3 run to have 115 stamina or more (35 to run the map, 80 for if the SG spawns). This is the tried and true method for pure powerleveling. The Sunday/Wednesday manyu daily advanced map is better if you're primarily leveling those colors; however XP gain for your own level (for free stamina/gather refills and more max stamina) is snail-speed (160 XP for 80 stamina, 2 XP per stamina. it SUCKS for increasing your own level)

As for leveling 3* and 4* girls, unless you go the whale route, as mentioned, new girls coming in will be REALLY slow paced, so the 4*s especially will take quite a while to be phased out of your teams. It does not hurt at all to level them. 3*s you might want to level only with manyus that don't match your 4*s (like if your 4*s are primarily Slice (red) and Hit (blue), then using a few yellows manyus on your Pierce 3* isn't a bad idea)

Once you've pumped up your levels, you can go ahead and try Ultimate maps. A strong helper squad goes a long way to getting map clears (usually to get 3* your own squads will have to handle a few tough fights on their own though).

Oh and to make the most of your helper squad, pick a single girl (highest rarity you have) and level the hell out of her (like every matching manyu you get) because your helper squad gets scaled down to the level of your strongest girl.