It is not like PAD where the good summons start at 5 or 6* and that is the only way you can get them. As far as I know, all of the best units can come in 3* or 4* form, so getting a 5* at the start just saves you an evolution or two at the cost of having a wildly impractical team cost at the start.Guess I gotta keep trying.
Check the evo charts for each one you get, the gimpest looking 3* can turn into the best units in non obvious ways. For example, leviathan turns into felneas eventually.