I agree with Daniel in that OCA and OCP Java is a good way to start. However it is not the only path that you can take.
Many books and resources can be found here https://coderanch.com/c/books
, some of them reviewed, but not all.
You may also want to check out the publisher's web sites for deals. For instance https://packtpub.com
some times has $5 deals and $10 deals on both books and videos.
I think that currently, for a limited time, there is a $5 sale.
There is also tutorials on Spring's own web site which may help out.
When you ask if it's worth it to get certification the answer all depends. Not all certifications are treated equally.
Some employers may think that certifications are not worth the paper they are printed on and others may expect some certifications.
Some people have too many certifications, and "too" is very subjective.
For the OCA exam I found that the journey which I took helped me to become a better Java programmer and a better programmer in general.
The certification is not going to change that and not having the OCP is not a hindrance to me (as far as I know) yet.
I too am learning Spring, but rather slowly at the moment as work keeps me busy. I would suggest you get a book/tutorial with has up to date coding exercises.
However everyone does learn differently so a good resource for me may not be a good resource for you.