You could likely start testing with $100. Propeller just emailed out a promo code as well so if you deposit $100 you get $125. Here is the email :
"1. Hand-picked profitable offers
To help you start easily, our partners from Zeydoo picked up 3 offers ideal for beginners and push traffic. Simple conversion flows and ready to use landing pages. Just create the link – and you are ready to go.
Virus Hunter 2020 – Mob apps
Girls Chat – Dating
TVBox – Mobile content
2. Advertising settings tips
Safe check
Push Notifications
This format has high CTR and can bring conversions on almost every vertical. Don't forget to use the In-Page Push to reach more audiences.
Read more –>
Safe check
CPC bidding
Pay for real clicks on your ads, not views. This will provide you with relevant traffic and cost-effective budget spending.
Read more –>
Safe check
Tier-3 countries
The easiest locations to start advertising campaigns. Algeria, Vietnam, Uzbekistan show the best conversions in May.
Read more –>
Safe check
Easy verticals
Dating, Sweepstakes and App Installs are considered easy-to-work verticals for beginners.
Read more –>
3. And... use a promotional code
Enjoy a bonus that will give you some extra budget for testing.
Deposit $100, use the code safe-start and get an extra $25.
Bonus is valid for the first deposit only. Offer expires on 25 May 2020.
Please note that codes are limited and do not work with Wire payments."
Depending on whether your campaign converts it's hard to determine how much you would need to optimize.