To start learning algebraic geometry:
First you should read some classical algebraic geometry, like in the notes by Gathmann (link). This provides an idea of the foundational examples and methods in the area.
At the same time, you need some knowledge on commutative algebra: Atiyah & MacDonald's book (link) will suffice. This is usually covered in Math 220B.
After you feel comfortable with the previous steps, you can start learning the modern language of algebraic geometry: schemes, sheaves and cohomology. You can follow Vakil's notes (link) or Hartshorne's book (link).
If you are interested in algebra (algebraic geometry, algebraic number theory, representation theory, mathematical physics, etc.), you should plan on learning this as early as possible. Every year we have strong undergraduates finishing Math 237 successfully. For Ph.D. students at UCSB interested in working with me, it is important to finish this by the end of your second year.
We have a weekly Seminar on Geometry and Arithmetic, taking place at 4:30pm-6pm on Thursdays, on topics related to algebraic geometry, number theory and etc. Students are strongly encouraged to regularly attend this as early as possible! Having difficulty following the talks? I recommend Vakil's "three things" exercise and other advice on going to talks.