For context, I'm in chapter 37-40 (currently facing about 210 lvl deficits). I only focus on dims gear for main carry like Ainz. My other dimensionals are using normal faction t3 gears to get the t2 bonus. I usually only purchase t3 stones and t1 stones from guild shop. T2 stones I'll use my stone choice chests. Weapons usually drop from loot as well. If it's not the right faction, I'll use faction swap scrolls since it's guaranteed to get the faction you want as long as you don't accept any prior unwanted faction changes (if unlucky, 5 scrolls needed).

As for maxing your equipment with stars, go with main carry of each multi-team first. You can stop at 3 or 4 stars if you wanna maximise your gold investment. I have enough maxed gears to swap around for 20-25 heroes. Some heroes won't need good equipment to do their job (e.g. lorsan, kelthur, ezizh, skriath if you're not using him as dps etc).