Trotting for grayling is great fun and you can do it quite cheaply!
Float rod, 13ft with a 2ft extension to make it 15ft, very handy on larger rivers, you can pick these rods up for around £40-£50 from masterline or ron thompson.
Reel, a fixed spool match reel will do, these can be as little as £15 up to £150, shimano or okuma are good reels, i used one for ages and still prefer it to my centrepin, load it with 4lb line or braid.
A selection of chubber floats, float elastics, quick change float connectors, lead free shot and barbless hooks size 14 to 22, a few spools of leader in 2lb, 3lb, another must is a bait apron/belt, that way the bait is easily fed into the swim and there is no messing about opening bait boxes etc.
After that all you have to worry about is sourcing fresh bait, white and mixed maggots, ive had days of 50 + grayling, you even get salmon, trout and sea trout occasionaly, trotting will outfish the fly any day of the week and its just as hard to master as the fly, its defo not a case of chucking in a maggot and pulling out a fish