In my experience, the best way to get better at math is to do a lot of it. Find some book that's "good enough" for some topic you're interested, and work many many problems from the book. You'll learn about the topic, but more importantly you'll learn problem solving skills. I recommend working the problem until you're sure the answer is right -- in grad school problem sets didn't have answers you could check, and full understanding was necessary to get the problem sets correct.

For me, a watershed book was Introduction to Analysis by Rosenlicht [1]. Proof-based, very "mathy", small and compact (so to speak) but with a massive scope. A great introduction to a really important topic, and it'll put your brain through its paces.

Again, I recommend working nearly every problem.

[1] https://www.amazon.com/Introduction-Analysis-Dover-Books-Mat...

Digression: Terry Tao wrote a book on analysis? That's awesome!

Recommendation: https://www.amazon.com/Introduction-Analysis-Dover-Books-Mat...

I wouldn't recommend Spivak for self-study and a first exposure to analysis. It's known to be notoriously difficult even for good students.

I learned from this Dover book[1]; I think it's pretty good. From there you might move up to Baby Rudin[2], but it might have a lot of typos, or big gaps in the exposition that are taken to be obvious but require several steps to fill in, since that was certainly the case for Papa Rudin[3].

[1]: https://www.amazon.com/Introduction-Analysis-Dover-Books-Mat... [2]: https://www.amazon.com/Principles-Mathematical-Analysis-Inte... [3]: https://www.amazon.com/Real-Complex-Analysis-Higher-Mathemat...

I highly recommend this book for Real Analysis http://www.amazon.com/Introduction-Analysis-Maxwell-Rosenlic...

We used it at the University of Texas at Austin for the first semester in Real Analysis. I found it very clear and easy to follow.