Since any time anyone bashes a manufacture 10 people will defend it I will just say what companies who's gear I no longer use or would not ever use.
Tilos, Oceanic, Aeris, Mares, Aqualung, Cressisub, Dacor, Bare, Genesis, Sherwood, Tusa and others.
Of those several make good stuff (oceanic, sherwood, aqualung) or at least some of what they make is good but I made a decision not to use it.
Some companies which I like are:
Scubapro, Dive Rite, OMS, Halcyon, DUI, Whites, Salvo, Oxycheq, Apollo, etc.
There are companies like zeagle that make great stuff but I just dont like it for one reason or another so I dont buy it but If a good deal came along on something I needed I might take it, ya know.
Brand is important but for me the biggest factor is durability, lots of the cheaper stuff it just that and will not last as long or hold up to punishment (not saying you should treat dive gear poorly, but stuff happens). And for me I like to have everything the same, as example, all the regulators I own are scubapro mk17/S600's except deco regs so I choose to avoid all other regs just cause I want them to match.
Another reason I avoid certain companies is because they promote Jacket BCD's and choose not to sell backplates. That is a big deal with me as I realized how much better a diver a person can be with the proper equipment.
shop around, dont be pushed into a sale, shop online too, and dont buy anything without checkin into it well before hand. I made those mistakes and had a full set of gear that I didn't like by the next season as I realized my needs changed.
If any part of your brain even remotely thinks it would be fun or cool to cave dive or do some deep stuff avoid all the bs now and start buying stuff that can be used for the future. A BP/W style BCD will grow with a person forever and is modular to any needs, a good diaphragm reg will work in cold or warm conditions and likely outlast many expensive piston regs but a cheap piston reg like a mk2 can be used for anything from primary backgas regs to 100% O2 deco gas if you move into tech diving, Jet fins or turtle fins with spring straps are easier to use and more comfortable (when used properly) than long split fins or huge blades and will likely outlast any other piece of dive gear, a dry suit can be adapted for use in any climate but is more expensive however you will realize that being warm and dry is priceless. the list goes on and on.