As other have said, I would get at least a 24 foot trailer.
It's great to have extra space in front of the car to make it easier to tie the car down.

You also have room to store other stuff that you might want to have with you (tools, coolers, etc).

My first enclosed trailer was a 24 foot and now I've upgraded to a 28 foot and love the extra space.
The 28 foot lets me have room to have the golf cart along as a pit vehicle.
The one thing that I wish it had is an escape door, but I'm planning on adding one at some point.
I added the awning last summer just before the Mopar Nats.

I don't know if you're looking at new or used but you can usually find a reasonable deal on a clean used one.
I got the 28 ft about 3 years ago and it had new tires on it then (cabinets in the front and a winch in it) and I got it for $4k which I think was reasonable for a clean used trailer.

To me it's tough to tie up a lot more money than that in a trailer that get used maybe 6 to 10 time a years.
It is great for storage also.