From how I learned, most easy seems to remember that
- A three note major chord can be built on any piano key by pressing additionally a key three keys up and then another two keys more up.
- A three note minor chord can be built with the opposite rule (first two keys up, then three keys more up).
You need to count both black and white keys. The keys that you actually press do not count ("two keys" I mean two keys = half tones in between, making minor third, and "three keys" is getting the major third). To make easier to remember, note that the distance between the two bounding keys is always the same, six keys, as they always make perfect fifth. Only the position of the middle key changes.
You can learn to find 24 important I would say chords this way in ten minutes at most. Then probably makes sense to read somewhere about chord voicing, also easy. 7th chords are not very difficult to understand but without voicing may be tricky to get on the keyboard.
Also, pressing every second white key, three keys in total, near always produces either valid minor or valid major chord, depending from root note (C Dm Em F G Am and only B/Bm must be picked differently, using one or two black keys).
Further is not so easy but I would recommend to try understanding at least some theory behind rather than just learning the positions of the keys to press.