Potty recommendations please?

My lo is nearly 18 months and is aware when she is going to the loo and asks to have her nappy changed some of the time! I don't think she is quite ready for 'training' but would like to have a potty in situ just to get her used to the idea.
What potty's do any of you recommend, this is a new phenomenon for me and there are so many!!

Thanks. xx