For learning beginner guitar chords, after getting the simple major and minor open chords under contol, you'll want to start adding 7th chords: dominant 7ths, major 7ths and minor 7ths. The chart on this page show you how to play a small group of dominant 7th chords (usually just called "7th chords" so a "C7" is a dominant 7th).
These 7th chords are very common in songs, and add an interesting dimension to music, often described as sounding unfinished or needing to be completed by a major chord.
First practice playing the D7, G7, and C7 chords and transitioning between them. Then add the E7 and A7 chords as well. A good way to practice is to strum each chord four times, then switch and four strums on the next chord, etc. A metronome is a good tool to keep your timing on track as you learn beginner guitar chords.