Help for a beginner

Hello! I’m planning to get my first pet fish. I’ve had experience with fish at a relative’s house, but never my own tank.
Tank size I’m looking at: 30L, 38 x 26 x 41.5 cm (L x W x H). But I can get a bigger tank. I’m torn between a fantail goldfish, or similar, and neon tetras. I know I can’t mix them because of different requirements.
Are either of those suitable? Also open to other suggestions that work well for beginners.

Thanks in advance for any tips!