I just started this game yesterday with Thor, and bought Venom as soon as I could and don't plan on switching any time soon.
I have been donating every item I get to Hank Pym the crafter in Hubs so far... I'm level 6 with him

What is the maximum level I can donate to these vendors to and who else is good to donate to for Venom? Assuming hank pym was a good choice, hopefully

The crafter is always the best to level first, followed by the enchanter. The maximum level for vendors is rank 20, which can take quite a while for a new player. Luckily these are all shared across your account. It's well worth the investment

Okay! Awesome.

Save up all of your uniques. Once you get to a certain crafter you can exchange a number of the same unique (3 for 50k, 4 for 200k, 5 for 500k) for credit chests. A 500k chest can get you from 1-17 in one item as a donation.

Should i wait to use coffer of achievements or does it not matter what level i am

It doesn't matter. They always reward level 60 gear even if used at a lower level. I would suggest you use it in a hero you plan on gearing up, but when you use it doesn't really matter.

I leveled them in 3 days including the most recent midtown monday @ 100% exp/rif/sif weekl had to be 20,000 clicks to get both to 20 off 3 sentinel dolls (made 1 gun) and all purples/blues/cosmics

Hey does anybody know which vendor? I have like 5 sets of 3 uniques. Tryna cash in

Crafter then enchanter

Crafter at level 16 can start making credit chests. It levels them super quickly. The grind to 16 is slow though