Personally I don’t like Bartok’s Mikrokosmos, so I do not use it.
For total beginner’s my favourite is Edna Mae Burne “A dozen a day”, which are nie exercises besides being excellent sight-reading material.
However, as soon as I can I will get away from this, since it is not real music.
What I use next is accompaniments.
Since I play the recorder, I will give my students the piano part (there is a variety of difficulty levels available). There are huge advantages to using this sort of material:
1. It develops musicality.
2. It is incredibly motivating, since making music together is a great pleasure.
3. The student learns that mistakes are of no consequence, the only thing that matters is to keep going.
4. The student starts to learn several tricks of the trade: Simplifying chords, waiting to catch up the soloist later on, understanding harmonic structure.
5. Since the melody is usually the responsibility of the soloist, the accompaniments are difficult to play simply by ear, so the student has actually to read the music.
6. The student will have to cope with 3 staves (two for the piano and one for the recorder), so his skill in sight reading will improve tremendously.
7. It develops everything: ear training, sight-reading, being in time, musicality.
I am surprised it in not used more often.
If you do not play another instrument, you can still do it by using the 4-hand repertory.
Best wishes,
Bernhard.