A lot of this gear is expensive and the OP has a budget of $300-$400 for tent, sleeping bag, and sleeping pad.

I'd hunt around for gear on sale; check out REI outlet and Sierra Trading post.

By and large you are not going to go wrong getting gear from reputable manufacturers.

This big agnes air core sleeping is $55.73 at REI outlet for example:

https://www.rei.com/rei-garage/produ...e-sleeping-pad

I like that it's 3.25 inches; I find a little thicker matters more comfortable.

For sleeping bags, I'd look at synthetic in your price range like this mountainsmith bag at $89.73

https://www.rei.com/rei-garage/produ...f-sleeping-bag

The weight isn't terrible either. That leaves you in the neighborhood of $150 for a tent if trying to get your gear for $300 total.

A lot of folks on BF like this Eureka spitfire tent; it's a good design. The 2 person (and you really want the extra space for a 2 person even if going solo) is on sale at Campor for $159.96

https://www.campmor.com/c/eureka-spitfire-2-tent