2 angels
24 tetras-3 shoals, 8 each
5 panda corys
Is this good out should I take out some tetras?
In the tank you mentioned (48x12x18 - 55G) I would happily go with 6x Angels, 3 shoals of tetras, up them to 10-12 and check compatabilities of the tetras (some nip, some will be too small etc), up the cories, you have the space for them and they will appreciate the numbers say, 15 of them? even after all that, you should be able to have spare capacity. Obv this assumes that you invest in a suitable filter

A dummy list would be as such:
6 Angels
12 Rummy Nose Tetras
12 Black Widow Tetras (unsure of their sitability, so check that)
12 Cardinal Tetras
15 Panda Cories
maybe swap out one group of tetras for something surface dwelling to spread the tank out a bit...