When I started to actively play this game, I got a starter pack as a gift from friend.
That was insta unlock of Proxy, Vassili, Sawbonez, Arty and Fragger.
With credits I purchased Sparks quite quickly.
When Phantom came out, I used money to unlock this smexy beast.
Also I unlocked Redeye with real money.
A lot credits I used for trading up cards and got already few cobalt cards and a lot nice golden loadouts as well. Gotta get some bling bling for my favorite mercs. 
Do you buy mercs with money or credits?
I can’t bring myself to support a micro transaction system in an fps. Have everything unlocked purely through credits though.
Credits are incredibly easy to obtain. I’m sitting on like 100k+ right now.
I’ve unlocked every merc I have (except Fragger who I got a free code for) with credits. Proxy, Sawbonez, Bushwhacker, Redeye, and Fletcher being the ones I’ve bought so far. The next merc I will buy is Stoker whenever he comes out, not interested in Phoenix at all due to Sawbonez being exactly what I want in a medic. Though I will likely have the credits for a loadout for Stoker as well when he comes out.
credits, and all are unlocked.
The game needs better monetized cosmetic customization at some point down the line for people like me.
I did buy the starter pack to support the devs and I thought the price point was what this game is worth.
after that credits all the way.
i mis-clicked in the vote tho. should be both since i got the starter pack
I bought the starter pack which was nice and I don’t mind supporting the devs and I bought nader because I got her as cobalt, really wanted to try that merc.
I pay to play 
I am able to support DB financially, and I will. I think its great that you can choose to spend real money or in-game credits to purchase mercs.