@kennethe62 So my advice for buying clothes pre baby is to not buy a lot at all and what you do buy should be versatile. Save the money you would've spent on clothes and wait until after she's born, then buy clothes as needed, only 1 to maybe 2 sizes ahead so you're not too caught off guard one way or the other. If shopping isn't therapy for you, you can even go to the sites you would've bought from now, save whatever your favorite clothes are now, and then when the time comes that you actually need those clothes, you can buy them in the appropriate size (so pick out some long sleeve onesies and a couple jackets, but don't actually buy them until August or September when you have a better sense of what size would be best).
If your baby is going to be born in summer prep for that. Short sleeve onesies out the wazoo. If you like to keep your house cold, you can buy sleep n plays, but if your AC is bad or non-existent, don't even bother with those. You will still want some pants because when you are in ac it can get chilly, and you can buy socks or booties for the same reason, but you don't need a ton. I would only buy a couple nb things if you buy any at all because they may not even fit. You can always buy more clothes after she's born if she turns out to be teeny tiny and being in one-size-too-big for a little while isn't gonna hurt her. I would mostly get 0-3 here in these warm-weather outfits. I would also get a few things in the 3-6 size following the same idea, but not a lot.
If your baby is average to large, these will cover her for most of the summer, and if your baby is teeny tiny the short sleeve onesies still work well for base layers underneath sweaters/jackets or sleepers. Regardless, the 0-3 month size should cover her for her first several weeks and then you can order/shop for more after she's born.
Definitely don't try to buy more than one or maybe two sizes ahead because it really is hard to predict not only their general sizes but also when their growth spurts are gonna happen. My son was born average, hit a basically never ending growth spurt around 6 months, quickly gaining percentiles until he reached 90th around a year, and has finally settled down and is heading back into average territory now at almost 17 months. Your girl may end up only being in 6-9 months for a month, or may stay in that size for 6 months. Additional complicating factor is that the way something fits varies wildly by material and brand. I can still easily put a pair of 9-month leggings on him despite having multiple pairs of 18-mo pants I can't get on him at all.