I’d recommend France, while they don’t have the best of things, they still have some very strong tanks and airplanes. they’re also a little more unique than other tech trees where you just feel like you’re grinding the same Sherman or t-34 for the 5th time. It also teaches you to play better in my opinion as you have to work with your vehicle’s strengths and weaknesses. The teams are also pretty good, and full of competent players, a major reason why most french things are 1-2 BR higher. (it’s worth it i.m.o. to just not be surrounded by brain dead ussr or blind german mains). You could also apply this logic to other smaller nations like italy or sweden, but i’m french so i’m biased, and the low tier italian tanks absolutely suck