You need surprisingly little to do a lot of things - if you went for top quality kit, the whole list below would cost less than £100. If you want bargain-basement, you'd get change from £40.
When we decided to stock an item it was on the basis of, first, quality and only secondarily, price. Now, your local hardware shop will appreciate your business, failing that a B&Q or similar. Or surf the net and take a chance...
Soldering Iron will cost from £10 to £25, we recommend Antex equipment.