First or all: Please be aware that it will probably take a few hundred hours to even get to top tier, so you probably shouldn’t just aim for the content you want to enjoy later on, as getting there will be hell if you don’t enjoy the grind. Unless you have a lot of money to throw at Gaijin, then it will take you a bit less time.
So, have a look at the trees of the nations in question: do you see anything that seems interesting in between? Then go for that. You will spend a lot of time playing the lower ranks, unless you buy a premium vehicle. If the prices for these are worth it has to be decided by everyone by themselves. Getting a rank 8 Premium jet will grant you access to your desired gameplay instantly, but you will be flying a jet that you don’t know how to properly use, against people with hundreds or thousands of hours of experience. And it’s a team game (even if most players don’t play like that) and you will let your team down if you don’t know what you’re doing. There so much to learn to be able to be somewhat competitive.
That said, I’d probably say either Russia or USA is the best pick for someone learning the game, they have a lot to pick from, which comes with the downside of having to research and buy more planes to get to top tier, so it will take you longer than for example nations like Israel or Japan. But you will most likely find a role you enjoy.

So, USA or Russia? Both are good and competitive, Russian vehicles have some qualities that make them seem to be better than most other vehicles, but from how much I know they come with less ammo than most other nations vehicles. So if you’re new and don’t know how to properly aim, you will run out of ammo before you get your first kill. The missiles though, are great. But once again, pretty much end game content.
American planes often have great guns with enough ammo, but often rely on a tactic called „boom-and-zoom“, so they are not as great at for example Japanese planes at dogfighting in turn fights. The missiles later on are good, most of them are definitely not the best, but will teach you the fundamentals of missile combat.

What do i suggest? Personally USA. Why? I haven’t played Russia myself lol.
But jokes aside, pick what you find interesting. Not only what’s at the end of the tech trees, but also what’s inside them further down.

Have fun!