Go with as big a tank as you can for these simple reasons.
1) Saltwater has many water peramiters that you need to keep in line. The smaller body of water the more these will fluxuate and cause an unstable enviorment for your creatures.
2) There is less disolved oxygen in saltwater as there is in freshwater so you can keep less creatures in the same size body of water as you can with freshwater. So unless your willing to keep 1 or 2 items in a small 10 gal
tank go with a 35 or even larger.
When picking tank size go with one that has the most surface area for the water/air gas exchange. Many tanks are sold in different configurations like a 20 Long vs a 20 High. Both hold 20 gal
but the long design is more desirable than the high design. Simply because it has more surface area.
If you want to maximize your budget I would first start off with a few good reference books. Thease books are great since they allow you a desk reference at times we are not around.
Specificly I would suggest the book Conscientious Marine Aquarist by Robert Fenner the first third of the book covers tank setup methods and various types of tanks like Fish only, FIsh with live rock, and reef. The last 2/3ed of the book covers different fish and profiles them in such a way you can not only see them but learn what they need.
One thing I would urge you to do is not become an impulse buyer of fish/creatures. Often times people will go into a store and see something that they just 'have to have' and they buy it before knowing the detials on its care and compatability. Often this ends up hurting them as they discover its not compatible with something else in the tank or its care level is higher than they are prepaird for or it needs a larger body of water than what they can provide.