I am no expert... But... I've been down the road for the last year trying to go the "Cheaper" route. I bought a 30g. tank with a HOB
AquaClear 70 filter, live rocks, live sand, and fish. Long story short, don't do it. And I would NEVER want to discourage you from going with the canister filter for a small tank. You can do that but your tank will never thrive. Been there done it, BUT!!!
2 nights ago I bought a New 65g. Deep Blue Pro, Reef ready tank and before that I ordered a Trigger Systems 30s sump. The setup cost me right at 400.00. That's tank and sump. I still probably like about 200.00 to get the hardware and plumbing... So 600.00 for a new sump and tank... If you go used then you can cut that price in half, 300.00... The initial setup is expensive for a Reef Ready Setup. But I really encourage you to consider #1, get the biggest tank you can afford/fit. #2 Save some money and go with a tank-sump-skimmer setup. You will save hundreds in the long run. I promise. I've wasted 500.00+ on my 30g instead of doing things the right way. But hey! Like I always say, it's up to you!