Blood Red Skies is a great game. Quick to play, easy to learn, hard to master, cheap to get into, massive historical depth if you like that sort of thing, looks good and loads of fun. Now lockdown is ending (hopefully) I think it will see a bit of a resurgence. I sometimes get asked about starting to play Blood Red Skies, so here is my brief suggestions about what you need.
1. A starter set is nice, but not essential. The old Battle of Britain starter set is now out of print, and the new Battle of Midway starter set has been delayed so often that there are now internet memes about it. Hopefully "soon". All is not lost however. Free pdfs of the rules are available Warlord site and Warlord have also bundled the excellent "Air Strike" supplement with a set of the game tokens. Air Strike is a supplement that contains the full rules plus loads of other "stuff" like attacking ground targets etc.
2. A Squadron. This is the first big decision, what do you want to play with? There are two routes to look at here. If you are totally new to the game, probably best top start with something "official" and buy a Squadron box from Warlord, which will include all the "stuff" you will need to run that Squadron. (A Squadron is usually six planes btw in BRS). If you want to go for something not available in Squadron boxes I would first check to see if the plane type you want is in one of the "Expansion" card sets - there are five of these, one each for the British, German, US, Soviet and Japanese, and each contains six data cards for planes plus and all the other bits to play them, just not the miniatures or bases. Somewhere in there your Squadron will be available, and everything in the expansions are covered one way or another by third party model manufacturers (almost).
3. An opponent, and you are set to go!
Ok assuming you did all that and want to go further, what is your next choice? I'd suggest a bomber squadron. Bombers in BRS usually play a secondary role to fighters. They're provided free as assets in scenarios and usually based around the number of "engines" - so six single engines, three twin engines or two four engine planes are used per Squadron. It does pay to pick a bomber type that matches your fighter Squadron, get something historically appropriate too. Trying to escort Mosquitos with Gladiators is not going to be easy :-). Personally I don't think you can go wrong with twin engine light bombers. They may not be the best from a defensive point of view, but they usually have enough speed to get to a target and just enough firepower to make attackers nervous. I am slowly building my collection and for each period of WW2 - early, middle, late, I plan to have at least one fighter and one bomber Squadron. For example my WW2 Soviets will have 3 each of Tupolev SB2 bombers for early war scenarios, PE2s for mid war, and Tu2s for late war. These are all twin engine light bombers and match up well with my fighter squadrons.
AND what to avoid. Ok this is just my opinion, but avoid metal models. They're too heavy for the game bases, so you need to put them on special base extensions. That in turn makes the game cramped to play (bigger bases) and it is just not worth the hassle, particularly as most planes are now available in plastic or lightweight resin from somewhere. Also replace the measuring stick thing that comes with the counter set. It looks cool but is a PITA to use. Get a third party one from ebay \ etsy or wherever, or just use a tape.
So there you go. Grab a Squadron and get into the cockpit - it's a great game. Hopefully I will see you in the skies!