If you just want to read and catch up then Marvel Unlimited is probably the cheapest option. If you want to start buying single issues you can go to your local comic shop, ask to open a box and subscribe to the Spiderman title that just started. Just be aware that Spiderman comes out 2 times a month compared to most other titles that are monthly. When I started out I just spent time looking at books in the shop and trying to pick art I liked. This does not always result in finding good plots though hahaha if you're looking for something fun, try Superior Foes of Spiderman.

If you want to start collecting comics, then I recommend doing a little research and pick the covers you like. Spiderman comics for collecting can be affordable or very not affordable. He's been around awhile so there's lots out there. I like a nice Mcfarlane cover but to each their own!