One of the greatest things about playing accordion is that there is so easy to find people to play with. Most people just love the sound and are happy to have an accordionist to play with since it seems exotic to them. It is also reasonably easy instrument to carry around.
My first tip to everone starting out is after you learn the basics, start playing with other people.
You dont have to start in a formal band just find a friend that play any instrument and team up with it. Myselt I have bought a cheap guitar that I dont play myself but is great for having when people are coming over. So many people know a little guitar so when some friend drop we often end up playing. It doesn't even have to be real song you play, just play around with some simple chords.
For example, make up a combination of C, G and F chords and play it around and around. Start taking turns improvising a melody on the chords. Just push around on the white buttons in the piano part and you will find something.
You are now officially improvising!