Wait you have a 20long, then I would say definitely try to save up and get the Remora or the coralife super skimmer. The Super skimmer being slightly better in performance, but a little more shotty construction and a bit more bulky.
If I were you though and knowing what I know now I would hold out for a sump either get a drilled tank (best choice) or a external hang on overflow (dont get cpr!), Get a nice return pump, then get a nice in-sump skimmer like a ASM G-1 or a Eruoreef if you can afford one. This will future proof you for what you and every hobbyist eventually does SPS corals. This way your not having to buy equipment, then sell it because you have and will change your mind on what you want to do, consequintly taking a big loss.
But if your budget is real tight and your impatient like I was go ahead and get a Remora, coralife super skimmer hang on.
Good luck with whatever you do though!