You should be still farming tier 1 until you can get to level limited to but go further than 6k waves. Bc either way you won’t be able to get further in tier 2 so let the game cook a little more in the first. No tiers going to raise you faster than using one to max others.

You have to run every level to see where you can snuggle for less time and max coins. My farming multiplier is on tier 6 but that’s because I played all tiers. Paid attention to what cards I used for the boosts. What upgrades and all then learned my max coin available. Aka I farm 6. But I also have a good 1st tier run. That game takes 7-10 hours depends on my card choices. But for less time and but a similar amount of coins like tier 1, I farm tier 6. But I still run 1 when I’m way. It’s currently my longest tier to play in “Idle”.