Depends what for.
Eurow Shag for removing wax.
Sealants/glazes ill use the yellow eurow detailer choice ones, you can pick them up in packs of something like 30 for 20 quid at macro.
Work ones, for polishing exhausts or doing other dirty work ill use anything i can get hold of. Homebase do 3 MF cloths for £1 those are ideal for cheap work.
Drying? Got to be the i4detailing ultra plush yellow £10 towels. Those are great, mine have lasted me over a year on clean water washes with no detergent and they are a similar colour to they are when new and work just as well, although they are starting to let go now so some new ones are on order.