i am f2p player i play cc about 4 months now i have micheal,vlad,dread drake,walla walla,skull knight,trixie are at 170 lvl and skill lvl 7 and i also have pd,cupid,mechtessa,grim fiend at 140 i am low on storage so i cant move my main heros to 180 so now what to do, is mechtessa,grim fiend worth for upgrade and i have also have aries,warlock,valentina at 100
Grim yes definitely, he is still a good hero. Make sure you can get his skill up.
I have a Tessa in a lower acc and she works well there, but i cant give you an accurate response since she is only 140 as well.
Aries is also good with a 5 revite, he he has that talent then he is good to lvl.
If you happen to save up enough, you should start with mike for 180+ along with SK.
I don't know your might, but if it is around 50k than you should start considering to evolve.
Make sure you have 5m gold (gold vaults to level 21), or gems (whichever you want to use), 400k Honor badges, and 550 flames. This is for 180+
After that you need, a dupe hero (or 20,000 shards), and evolution ruin (1,000 fame), and 1,000 red crystals. Thats what you need to evolve. I would evolve at or around 200. You get Blessed Tome 1 books depending on your hero's level after (I think) 185 (correct me if I am wrong :dizzy and with any might those books are helpful.
Sorry is you already know the evolve process, but if you didn't than I hope this helped.