If you don't have a following yet, (and I'm not being mean here--just direct), it doesn't matter. The point of a certain release schedule (one week apart or one month apart are typical) is that your book would rank because your mailing list bought it and it will stay visible for some optimal time as a result. A new book by an unknown author is going to, short of a miracle, sink to # 3 million faster than you'd like, and that sort of ranking will never let you be seen by people browsing for books. Of course, AMS ads have bolixed up the possibility of being visible through ranking alone. Sadly, you used to be able to win visibility on merit, but Amazon, wanting to line its pockets more than it wants to please customers, has the vendor's spend on AMS determining visibility more often than not. Visibility used to = more sales, and you could hang out for a while in the top 1000, assuming you had a purchasing mailing list. Even 300 people buying would start that process working. (I used to release at .99 to start the ball rolling and reward my mailing list for their loyalty.) The ultimate goal was to hit the top 20 in your subgenre, and that would help book browsers see your book easily. The top 3 in a subgenre was golden. I've been there, and it takes a good long while for the sales to tail off after that.
So these awful new days, with a new author, it'll be tough to sell any books beyond friends and family. First, have a great cover and great product description. What I'd do is put them in Select, so you're in KU/Amazon only. Release the first ASAP, and then release the second in 83 days more or so, at which point, you'll put the
first one to a five-day FREE sale. (that's under promotions). Then re-up for a second 90 days in KU and run another 5 free days as soon as they'll let you. So your first book is up there for 10 nearly consecutive days for free. For two days of that first five-day period, run promos at sites like Freebooksie and EReaderNewsToday if you can (they may require a minimum number of reviews). They'll run you about $60 each but get you a lot of downloads of the free book. If the second book is priced at $3.99, and if you spent $120, you'll need 45 sales of book 2 to make that work financially. Then hope that word of mouth takes over and keeps selling the book for a few months. If that does happen, and once you've paid for cover and editing, then look into AMS ads, keeping a low spend every day ($5-$10) for about two weeks. Then shut AMS ads off. Then six months later, do that all again.
If you can't afford those two ads, or if you don't have the reviews to get those good ads (it's competitive), then look through this list for free listings of free books:
https://kindlepreneur.com/list-sites-promote-free-amazon-books/ I'm not sure each still exits, so you'll have to work that out for yourself. Each one might not get you more than 5 free downloads of book 1, but if you get some reviews out of that, then next time around, you can get into the more effective sites like freebooksie.
Never put the second book to free--or even to .99. People who tell you "July is a bad month to release" or "X is a great month to release" don't know what they're talking about. Any month is a fine month and gives you an equal shot as any other month.
Good luck on learning the ropes of placing ads, and good luck on getting back to writing more. I wish you success.