To be honest, for a newbie/novice car cleaner, 90% will be down to the effort of doing it, rather than the quality of the product.
Elbow grease costs nothing as has been said.
Personally, as a guide (having not seen the car mind!)
Give it a good hose down and wash off
Wash it once more if really filthy. Dry.
Clay bar the paintwork - will remove the contaminants and make it easier to polish as well
Polish the paintwork, depending on the 'polish' and final wax coat to protect it would be a good idea
Clean the wheels and tyres, polish the wheels and dress the tyres.
Hoover the inside thoroughly, wipe the dash/door cards down with a mildy damp microfibre. Clean/treat the leather.
Clean the glass, a couple of times if it's in need of it.
There's other stuff you can do as/when you've got the time/inclination, but that's a good start there. I reckon you could make yourself a reasonable cleaning/polishing kit for £50-100, depending on the products you choose.
Halfords have had a 3 for 2 on cleaning stuff for a while - applies to all brands IIRC too
I recommend:
Meguiars Gold Class shampoo (£15 for a reasonable sized bottle)
Liquid leather cleaner/conditioner (about £10 for the pair, not in Halfords etc though)
Mequiars clay kit - used to be about £15 but I think it's changed now?
Autoglym interior shampoo - for general interior cleaning - not expensive
Polish/wax is a personal thing and there's loads to choose from. Gold class wax not great, doesn't last very well for general use. Perhaps Autoglym 'Super Resin Polish' as a good general polish for a newbie, can't really go wrong with it
Don't forget the before/after pics
No need to spend £££s unless you're really into it. Oh, and try and get a 'wash mitt', much better for your paintwork than a sponge
Will