I dont know about oldest but ive been using adbtc for years and personally my favorite since I just take 10 minutes out of my day to earn 500~ satoshi then use it in my advertising balance.
Interesting, I may give a try as I am looking for visitors. Does the traffic convert ?
Yes, back in 2017 i just spend my income from clicking ads and then use it for advertising and got tons of referrals, I'd say if you dont use a mainstream faucet to promote your link you should get a decent amount of referrals.