There are a few things you can do. I suggest going for mobile when you start.. It works for me. (Cant post links because im new, just look 'm up)
Facebook - I only recommend it if you're doing a "clean" campaign like Shopify using E-commerce stores or Teespring. You can also run gaming and lead gen offers on
Facebook. DO NOT do Facebook if you're running anything dirty. Your account's going to get banned and it'll be difficult for you to get another one.
Native Ads - Native is expensive for newbies, but if you’ve got a good budget ($3-5k) there’s a lot of potential. Native traffic sources like MGID are good.
Adult - Places like TrafficJunky. This vertical is super competitive - I’d recommend staying away as a newbie.
Mobile - The perfect place to be for newbies. There's so much volume coming in each day, and so many traffic sources.
There are different kind of mobile traffic sources:
Push
DSP
Pop Unders
Redirect
Here are a couple of big mobile traffic sources to get you started:
PropellorAds (huge volume on here)
PopAds
Cheers, good luck