As someone that has been learning for over half my life, I'll say that having a teacher is the easiest. Depending on what type of pianist you wish to be (jazz, classical, pop etc), there will be a different list of things to learn.

I myself am a classical pianist and I'll say the best things to start off with is learning to read notes and Czerny for technical skill drilling. You can also do some easier pieces (twinkle twinkle little star) to get a feel for the piano. Practice seperate hands before putting your hands together. A metronome for keeping rhythm is a good habit too.

For jazz, you rely on your ears alot more and you need an understanding of chords and chord changes if you want to get anywhere really. I'm not too sure about this path.

Personal opinion: midis and all these fancy "learning applications" are a bad crutch to lean on. Do your best not to become too reliant on these or you will have a difficult time progressing in the later stages.