i would say its only worth purchasing the grow packs if you cant get hold of a pressure cooker as you will need one and there quite expensive, also the boxes will give you enough to play around with if its not something you want to do more of in the future, but you will

i prefer wbs tek(WBS = wild bird seed)

its easy enough and a few super simple steps will guarantee good clean colonization near on every time without need for hepa filters or glove boxes

as for buying supplies there's only a couple things you need spores are easy to find all over the web everything it totally legal things like wild bird seed, straw like animal bedding, coffee filters and some decent silicone all costs near nothing though spores can run between 2 and 20 pounds depending on who has them in and how many are about at the time

i dont want to say to much as i am unsure on the rules for talking about mushrooms on this forum but if you search WBS tek im sure a shroomery link will appear.