Hello Dawn here,im going to start with basic and work my self up.i am going to attempt to make my own birthday cake for my daughter ofcourse has to be pink and princess err so baking wise what would be best square or round and what is the best food colouring do I use as asda all supermakets are dull. Sorry so many questions . Im a beginner also make my cakes in boxes wish me luck lol xx and thank you

Good luck!  

I'd suggest round pans, I think they're easier to work with.  

For coloring, I use Americolor, because I like the squeeze bottles, but Wilton has great options that should be available in any craft store such as Michael's, Hobby Lobby, etc.  A word of caution, pink is a color that stains and tends to get much deeper after sitting, so start with small amounts and work up to just below the color you want.  

There are many ways to make pretty pink princess cakes fairly easily!  Do a google search and you'll likely find step by step tutorials as well.