Starting out with a reasonable expectation of success.

[Sk8r]

1---read that sticky SETTING UP before you even start to acquire equipment---
2. if you just want to get your feet wet in the hobby, an all-in-one 29 gallon, at about 300.00 is probably the best turnkey (ie, ready to run without buying more and more pieces) going---because if you try to back your way in piece by piece or start too small, it's probably not going to go well. Best deal of all---get a used one.
3. If you want to go for it---get a 100 gallon with a 30 sump rig and enough light (T5s) to let you do coral if you decide you want to.

Very small tanks (10 gallons, say) are insanely hard to keep as saltwater: the salinity can change on you very, very fast, and there's almost nothing you can keep but shrimp, crabs, snails and corals---IF the light is good.

You can do a 30 with a Penguin filter if you limit yourself to a couple of the smallest gobies, have mostly crabs and snails and such, and don't mind a little algae. If you put a 6500 k CFL flood shoplight on it, you MIGHT get it to support mushroom corals. I've run one like this back in the day, and it was a nice little tank. Problem would be trying to push it to anything more than that.

In terms of 'getting your feet wet' with an upward expansion path, you could start with the 30 gallon Penguin tank, and if you like it, you could then use it as the sump for that 100 gallon monster tank, or at least a larger tank. Just figure how you're going to partition the 30 for a return pump and skimmer---and [hint: use a plastic box as a pump chamber: just sink it. Just needs to be a little shorter than your water line, to keep the pump fed. With an ATO (autotopoff).]

I think it's sensible to realize from the start that this isn't the cheapest hobby you could pick, but if you're careful about the upgrade path and most of all if you don't get the big-eyes for a critter you can't keep safely or healthily in your CURRENT tank---you can start small and inch yourself forward by smart planning. You can educate yourself and buy good used stuff as you find it. But most of all---keep what's appropriate for the tank you have now. That way you don't end up with a bad experience, and you can have the fun of planning your next step with a good vision of what you need.

[homer1475]

Just curious, but why the plastic box for the pump chamber? Vibration cracking the glass? Since I am currently planning out a bigger tank with a sump.

[Sk8r]

Just easier to get a containment in an already functioning tank, converting it to a sump with fuge. Otherwise you want to partition the tank with hard barriers, to keep fish, weed, snails out of your pump chamber (fish do manage to get down the overflow pipes. Dropping a proper-sized box in can create a chamber without the fuss of gluing baffles. It's not as nice as a pre-done factory assembled sump, but it's very straightforward and it works.