The approach I took was to start with the $20 plan, then when it became clear it wasn't sufficient I upgraded to the $100 plan. The $20 plan didn't cover one night of coding. With the $100 plan I started bumping into the 5 hour usage limits after ramping up over a week or two.

My average API equivalent use is around $30-40/hr. I would just bite the bullet on a plan for one month, then use that to calibrate your expectations around usage and cost optimization. The plans are heavily subsidized.

Thanks for the insight! Really wish they had easier cheaper ways to learn.