You can start with fish only with live rock and then move / upgrade to full reef as your budget allows. You wont be dissappointed if you go with a saltwater tank. A fish only live rock setup say a 30 gallon would probably cost around $150 more than a freshwater setup, you would need around 20-35lbs of live rock/base rock that is 6.99/lb (live) and around 3.99/lb (base), then salt around $25 for a bag that would do 50g, and a powerhead to circulate more water (price varies but generally $25-$65 can go up to $300+). The rest would be the same stuff you'd use on a freshwater tank. Of course there is plenty of upgrades availible that would be beneficial to a salt tank that are not really applicable to freshwater.
Once you get the FOWLR
set up then work on buying a protein skimmer, then maybe a RO
filter, 4 bulb t5ho or led
light, then possible a better filtration set up like a sump or a cannister filter. Then you would be ready for a reef setup, and you would have a good feeling for how to take care of the tank because the saltwater tank will require a little more maintence.