Only just read this thread.
If money is an issue, rather than colour at home, you could get your hair professionally coloured at an in-salon training session or a hairdressing training college. They usually charge a lower fee to cover the cost of products used and the students are supervised. If you can choose to book into a level 3 class, it should be better as the students will be already qualified hairdressers at level 2 and will be aiming to increase their skill set.
If you live in a main city, you can also try the Colour House training academies such as Wella Academy or L'Oreal. Toni & Guy, Hobs, or Sassoon academies in London.
I trained at Sassoon in London and the Academies offer loyalty schemes for regulars for cuts and colours and it's a real bargain. The downside is that you need to allow a lot of time for an appointment (2-3 hours for a haircut) as the tutors have to check the students progress regularly.
From an experienced hairdresser point of view, please don't wash your hair with baby shampoo or [shudders] fairy liquid. Your hairdresser has given you poor advice there! It will strip your scalp of natural protective oils which helps to stop your scalp suffering during any chemical service. If you have a build up of products in your hair, you're better off using a decent chelating shampoo designed specifically to deep cleanse the hair.
Baby shampoo is vile stuff. It's ph balanced to match tears so that it doesn't irritate the eyes but it's far too alkaline for hair, not gentle at all!
Hope this helps. :-)