You have to get defo some books in Analysis, Topology and Algebraic Geometry. My particular recommendations:

1-Algebraic Geometry, Robin Hartshorne.

2-Algebraic Geometry: A First Course, Joe Harris.

3-Commutative Algebra: with a View Toward Algebraic Geometry, David Eisenbud.

4-Complex Analysis, Serge Lang.

5-Advanced linear algebra, Steven Roman.

6-Linear algebra done right, Sheldon Axler.

7-An Introduction to Homological Algebra, Joseph J. Rotman .

8-An Introduction to Homological Algebra, Charles A. Weibel.

9-Categories for the Working Mathematician, Saunders Mac Lane.

10-.Introduction to Real Analysis, Christopher Heil.

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This should do more that 400 euros. These are the books I personally would never skip. Feel free to change my recommendations with other books you might prefer about these topics. Best editorials to find these are Springer, Cambridge, Oxford, Wiley, Princeton, AMS, De Gruyter and CRC Press. There you can find more. Also, I recommend to buy the books directly from their websites as there it will be cheaper than in other places. Enjoy your travel through the beautiful world of mathematics!