I competed up to the now 2*L level without tails. I think I was the only one in the dressage without tails, but I was 16, broke, and it wasn’t against the rules so I went for it. I also did not have the money for a top hat so it was kind of a win win. I remember saving for my first set of tails and my top hat, both bought used, and was so freaking excited. I still have the tails though if I get back up to the level again, I’d prob go with one that isn’t so heavy and wool.
I had a very reactive mare that would not tolerate the flapping of tails. She went ballistic when I tried so I went in a short coat. So yeah, make sure to practice in them before.
I will say one of the girls stabled near me at my first FEI was eliminated because she did not check the FEI rule book for allowed bits between USEF/FEI so please make sure to read up on the rules. Good luck!