Additions needed for a small project

I need some changes to an existing website. So i have created a very basic user system for the additions i need. I need 2 things making; 1. Jquery button submission, with no page refresh. 1a. User registration which allows for multiple errors (empty fields, non matching password field & less than x characters). 1b. Button submission for an increase/decrease of a value along with a success/error message. With the updating of a value displayed elsewhere on the page. 2. Paypal donation with values pulled from a MySQL database. 2a. Depending on which donation option a user has selected. Upon payment they will receive 'x' of what they purchased along with information inserting into the database (eg. User id, date, amount) I will send across the basic user system to the selected freelancer and they will build upon that