Hi
A few years ago I picked up this delightful instrument having put it off for years.
You will find everything you know from the site called mandolin cafe.
What you aim to buy depends on your budget but if you are going to play celtic music I would tend to an A style mandolin which will be cheaper so you will get a better quality at a lower price.
PM me if you would like to discuss anything. They are a bit like Kilts so many options and accessories to drive you slightly insane.
First up will be to learn Flower of Scotland, of course!