Is there any way to get Special costumes after the banner ends?

The costume gacha SUCKS and it's super hard to get enough rainbow cubes to even pull ONCE and whenever l do it's a fucking common costume that l already have. I want the special costumes but it's impossible for me to get them in the banner time [or at all] as a f2p. Is it possible to get them on the regular gacha or any other way?