I'll tell you my method, usually around 1.2K tokens a month, only paying 5 usd each time.
So, the majority of tokens I get are from the 30 day pass, 750 a month if you login daily. I then get 10 a day from my dailies, which is a little under 300 a month. I also do raid which gives around 450 tokens a month if I make top 500 each week (use a boiler mech!). I also watch ads daily, if I watch 4 a day that's 250 tokens a month. I also take advantage of events such as portals or special quests to get tokens. If you have a good foundation of items this stuff should be easy to do, it's just become a part of my routine at this point, click this button come back a few second later etc, I don't really need to pay much attention.
I know the math doesn't add up, but the numbers I gave are just rough estimates I'm actually too lazy to fix it.
tl;dr
- 30 day pass
- dailies
- raid
- ads