Hello HanKai,
First let me advise you to learn the basic tense that will let you talk about everything, and will open the comprehension of other tenses: present.
After understanding the rules and morphology of present tense, go for pretérito indefinido y pretérito imperfecto.
Aprendo: I learn - presente
Aprendía: I was learning - pretérito imperfecto
Aprendí: I learnt
Bonus tense: futuro - voy a aprender/I am going to learn
Cheers!