... you would recommend I definitely buy from a manufacturer like RealTraps, and what sort of other acoustic treatments are fine to construct on my own?
If you go to ethans site and read his descriptions and look at his plans, it is easy to construct your own.
Problems is that it is work, and they take up space.
For my studio I used Ethans plans and hired 2 union stagehand carpenters, borrowed a scene shop while the theater was in production (so the shop was unused at that time, and we worked one night..) built all the boxes for the traps and cut the faces, and built all the trays for the absorbers. (I chose to build the absorbers into wooden trays to provide a nice way to screw them into place. Wrapped the 703 with unbleached muslin at 88 cents a yard from Walmart, glued them into the trays that I had built and painted the same color as the wall.) Took the boxes back to the studio, sealed all the seams, stuffed them with 703, put a barrier to prevent the 703 from sagging into the face, calked and air-stapled the faces into place, and put them up. My total cost was around $1500 for a boatload of traps and absorbers.
One caution.... everyone wants to use foam. Yeah, but foam performance degrades significantly in a sharp downward curve from 250 cycles downward. Small rooms like home studios have frequency problems in the areas of... you guessed it... 250 cycles downward.
You don't have to spend a lot of money to get a decent sound, but you can also cheap out, make moves and spend money without thinking, and screw yourself baddly.
First watch out for the deal of the day, second watch out for the product du jure... have you noticed that todays GOTTA HAVE IT product is sitting on the used equipment shelf 10 months from now? I have made it a point to buy proven products, I seldom am in a hurry to buy (if it is great today, it will be just as great tomorrow), and I never believe manufacturers promises.
A 'room kit' from Real Traps is probably around $2300 +/-. I bought one a few years ago for my apartment writing room. It was sure nice to just unpack the boxes and hang the suckers up. Of course, I didn't get near the number of traps that I built for less money, but this was an issue of convenience and speed. Very nice, and I have it in my attic music room now, and it will follow me to the new house we're buying this summer.
Point being that if you read Ethans writings he will point you to the low cost or free gear to determine the problems in your room, and you can explore solutions to fit your needs, rather than just punt and hope you got it right.
If I was recommending a low budget system today, it would probably be based around Magix Samplitude (the entry level version for about $80, which has an upgrade path all the way to their flagship Sequoia which is around $3k ), one of the RME cards...likely the Multiface which is decently expandable. I'm not up on cheap full range monitors but when I was, nothing touched the Mackie HR 824 in their price class, and nothing cheaper was worth buying. There are just too many great mic pres in all price classes over $800, but I would not buy any mic pre for less than that.... simple low budget consoles offer similar sonic performance plus all the benefits of the routing and more channels. Cheaper pres are mostly a marketing issue, not a sonic one. I really stress good mics and waiting to buy them one at a time and getting them used can really be a benefit. But if you cannot wait, Studio Projects offers a number of affordable options and the company seems to stand behind what they build. Personally I prefer stepped attenuation for monitor control, to allow for consistent and repeatable settings. I built my own using Forssell op amps, and it ended up costing close to a grand. The fantastic Cranesong Avocet can often be found used for under $2k. You could build a cheaper one using parts from Gold Point or DACT, and only be into a couple of hundred dollars, maybe less.
My writing room has 2 channels of John Hardy, a 2 channel Great River NV, 2 channels from an old DataMix console (Electric Ladylands original consoles were DataMix), and 2 channels of Midas XL4 with the eqs. Nothing in the megadollar pricerange, but all quite respectable. There are so many choices though, and I could start listing them and it would just get stupid. A little Mackie console is likely a better deal all the way around.