As an instructor I’m a somewhat experienced diver that has tried a few different sets of gear in the years I’ve been diving. I’m not employed by any diveshop that sells a particular brand. I’m someone who is active on a few scuba forums. So I often am confronted with questions from other divers regarding what gear to buy.
This subject is impossible for anyone other than the individual diver to answer completely. It is highly dependant on the intended diving profiles and personal needs. For the beginner this leaves a lot of flexibility in choice. The more advanced divers involved in more specialized diving may have stricter requirements but the following still applies:
As for brands many of the well known brands have models that would fit your needs. May I suggest that you vote for a free market with your purchase. Give the local dive shop a chance to serve you and match advertized prices. Some may surprise you. Online dealers are an option if you already know what model and size you need but make sure they are authorized dealers for the brand you are buying if you want a factory warranty. Grey market is fine from a reputable dealer that stand behind what they sell with their own warranty.
Please avoid the manufacturers that require their dealers to sell for Manufacturers Authorized Retail Price (MARP) This is nothing less than legal price fixing. Many well know and highly regarded manufacturers use this technique to artificially maintains the high price of their gear.
Instead seek out Brands that use MAP pricing Minimum Advertized Price. This allows the dealer to set the price they wish to sell for. It only requires them not to advertize a lower price. This allows you to stop in or call and negotiate the best deal you can. It can save you some serious coin when shopping for scuba gear. Don’t let anyone convince you the best brands don’t negotiate it’s just not true the top MAP brands offer models just as good as the MARP brands and in many case superior models are available at discount from authorized dealers.
Case in point Oceanic EOS and Sherwood SR-1 are 2 of the top rated environmentally sealed regulators available (So good that in blind test divers are high unlikely to be able to tell one from another or from regs costing twice the price) There are plenty of other examples in other equipment categories.