Hindsight is 20/20....knowing what I know now, I would have purchased equipment that would help me go all grain sooner....but there is something to be said about getting the minimum and just going for it. Just get brewing....
but...
If you can find a decommissioned keg and cut the top off of it, that would be way cheaper.....and then buy a step bit $17 and a weldless bulkhead and valve and you have an indestructable 15 gallon stainless steel kettle for almost nothing.....that would have been cheaper than my 5 gallon pot when I started. A keggle (as we call a converted keg to kettle) can later be retrofited with a false bottom and be used as a mash tun, too. In my opinion, this is the way to go.
Get the 7 gallon carboy, skip the secondary (or any 5 gallon capacity), or go with a better bottle.....or find a decommissioned keg and cut the top off of it (note the theme here)....I open ferment in a cut open keg (without any other fittings in it)....had I been smart, I would have skipped the plastic bucket years and then 12 years using carboys....I do use my 5 gallon pot's lid to cover the hole in the keg....so that kettle wasn't a total waste.