Good rule of thumb, taught to me pretty early- add smallest and most peaceful first, usually a mid level schooler. Next, once the tank has a chance to mature, add your peaceful bottom dwellers (for a 25g with a school of bloodfin tetra I would look at smaller cory cat species- though hasbros and pygmy are not really bottom dwellers And not so well suited for beginning aquarists). Give the tank a chance to adjust to that addition and monitor parameters. Then comes filling in with peaceful schools and/or planning for the addition of a feature fish/pair.
To me a 25g with bloodfin tetra screams give me lots of plants, 5 panda cory and maybe a trio of dwarf hatchets.