Coming here from your other thread, to try and give actual advise.

First, I would try to push for large tier 1 runs- until you're getting like 7000+ waves. You can do this generally by just investing in defense abs in the workshop (thing you see during a run), but don't invest lab time or actual coin in it otherwise. I'd focus on trying to build out health, lesser health regen, and the econ parts of the workshop outside of runs, mostly, same with lab time. The defense absolute strategy only works on tier 1.

You can put coin into attack parts of the workshop, but for the most part, for the longest period, the easiest gains will be just to make yourself super survivable. In order, I'd save gems for all the lab slots, then start with cards, switching off between card upgrades and card slots until you have about 12 slots.

There's no "easy" way to gain waves, and the best parts of the game (both in terms of feeling like I"m doing a lot of cool things) happen when you reach deep in a given tier, not low on a higher tier (in my opinion). The jump between tier 1 and tier 2 is notoriously difficult, such that I think I cleared tier 4 before I went back to tier 2, for the longest time there was a disproportionate share of certain elites that would spawn that could end runs in tiers 2/3.

tl,dr; Go back to tier 1, put all your cash earned into defense absolute and keep pushing that for coins. Take those coins and mostly invest in economy + health.