I haven't experienced any real issues with GPU availability on Colab, I suggest that you just go ahead and use it and wait with the premature optimization until you actually hit a wall and need it.

For general advice focused on beginners and ESPECIALLY practical, cheap and efficient methods and hacks to do DL, I recommend searching in https://www.fast.ai/ and their forums https://forums.fast.ai/

I'll try to search inside fast.ai if there is a more specific link to give. I know that one of their chief pieces of advice has been to use Colab and take advantage of the 300$ free credit you get (per credit card) when signing up to Google Cloud, which you can use for DL.

Disclaimer - I'm one of the creators of DagsHub, we created the platform especially to help people like you with the difficulties of managing things like data and model versioning, experiment tracking, labeling, etc. we'd love to have you onboard, and thanks for reading until the end :)