Hey mate, welcome back to the hobby and to the forums.
First, I use this site all the time for my kits and supplies
http://www.scalehobbyist.com/index.php
their prices are very good.
As far as what to stay away from well... it depends on your skill. Trumpeter and Academy have some nice variety of kits but there can be issues (im always finding issues) like gaps and such, that require alot of work to fix.
Tamiya are nice, there simple kits, most stuff is molded on and the part list is normally low and there not that difficult but they dont look as good as a better quality kit.
Dragon kits are very good for plastic kits, close to top of the line if not, tons and tons of parts tons of subjects, photo etched, etc. The figure kits are some of the best you can get without getting resin.
I haven't done or looked at any NEW Italeri but I the old ones are alright though there not the most detailed and require a good bit of work.
Cant attest to Mini art either, though I have done their buildings and there the most frustrating thing (there vacuform, the vehichles are not) but after the work the finished product is always beautiful.
Master Box is alot of different types of vehichles, havent built one of their vehichles, but their figure kits are gorgeous, very nicley sculpted and the poses are dynamic and unique.
For Revell I would throw them in the same category as Italeri, except I have nothing but bad luck with their kits (even though there the old ones)
Cyber hobby is on par with dragon for vehichles
I only have one kit from bronco but its a nice kit, comes with a few Pe parts which was suprising for the price I paid for it.
as far as supplies it depends on who you ask.
For brushes I just go to Michaels or AC more and buy one of those 6 packs of brushes and they work beautifully for me.
I love Tamiya acrylic paints.
I like model master paints but sometimes there not the best, but there good paints for Enamel.
Testors is alright but there not the best at all, and they dry up fast.
Humbrol is an odd type, come in little paint can like things but I find their colors to be very nice.
For primer I would suggest Tamiya extra Fine Primer, if you can find it. Every site I look at has it discontinued but its the best I ever used.
Testors primer is alright but it can sometimes come out to thick, even after letting it soak in hot water and shaking it thoroughly to mix it up.
I suggest using a laquer for dull coate or clear coat, or any kind of sealing. It allows you to use enamel thinner if you need to do more stuff over top, like washes, without hurting anything under it.
On that note, use laquer thinner to clean your brushes, it eats enamel acrylic and laquer and will even clean artist oils off of your brushes.
I cant give much advice on airbrushes, I have a badger 200 NH (new head model) I dont recommend it, I have had nothing but issues with it.
Squadron white putty is great for filling seams.
While on filling seams lets talk about glue
testors red blue is what I use when I have seams I need to fill, it melts the parts it touches allowing them to dry together as a whole, which allows for easier puttying and sanding, meaning there is no gap anymore, not just some glue between the gap.
for places you dont need to fill seams OR small parts I recommended Tamiya Extra Thin Cement. I swear by it.
I get my super glue from the dollar store, and its super glue brand super glue.
If im forgetting anything I add it later, hope this helps