I'm studying German for a while, I know I still have a lot to learn. But I'm considering which verbs tense I should learn after Simple Present, like a study guide for verbs tense. Could someone give me a help?!
Well, there's not really a rule in which order you should learn tenses, but in general–disregarding the actual language–I would learn both a future and a past tense. That basically allows you to convey if something happened in the past, happens right now or is going to happen.
Luckily, in German you can express future with Präsens. Thus, you can focus on the past tense.
As Emanuel correctly mentioned, in spoken language Germans mainly use Perfekt. I am of the opinion, however, that you shouldn't ignore Präteritum because this is used in written text very much. Since there's technically not really a difference between those tenses (both refer to a finished action in the past), it's not a real overhead.
The answer is simple:
Learn the spoken version of the past tense. And do NOT learn the preterit.