Outdoor is much cheaper.
While indoor start with your 1 tent and don’t dive in to deep, get a grow or two under your belt indoor.
Gorilla tents are nice but not worth the price anymore they have good height to them.
Make sure your buying the tallest tent you can most often height becomes an issue once all the gears in it.
To start I would recommend a 2 in 1 tent something like the topogrow 60"X48"X80", Amazon it. I have their 3x3 version. It gives you a little side compartment to start plants in or organize gear etc etc it’s nice I wish my first tent was a 2 in 1.
This gives you the ability to do 4 plants as a start
Edit: forgot you had ballast and gear… @KeystoneCops can help you there, that being said aside from easing your start up costs I wouldn’t in the future invest in CMH/HPS systems due to led technology /efficiency and they are safer fire hazard wise.
To light the 4x4 I strongly recommend, and I think our lighting guru @dbrn32 would agree two of these will be a great choice you won’t regret.
Unless you want to build your own and save money, you sound hands on and totally can it will save you money and give you just as good of a product. For that head over to the lighting threads and go to the “let’s TALK DIY lighting” thread. Let's talk DIY lights