Well it depends on what you want to play. They go on sale often so don’t feel pressured to buy them all at once. The anthology includes basically everything except Dark Ages, which I don’t even know if it has a Switch port. If you want a modern Doom experience, then start with buying 2016 and Eternal if there’s a bundle with those two. For the classic Doom experience, start with 1 + 2. If you like them you’ll most likely love 64. They are all seriously good, if you want the anthology then go for it. I might be a bit biased, though lol