If you do a 20 30 or 40 get a breeder tank this is going to help you. Gives you alot of room for you to work with. Check out craigslist or maybe a state forum. We have one im from kentucky its called "Big Blue Reef" you can get great deals from them. Also keep track or petco the have the $1 a gallon sales every now and then. I dont think you can get a 20 breeder so count that out for your dt (display tank) get a 20 long for your sump.
Filteration: the main filtration of your tank is going to be the rock, this is natural so your going to get about 1 pound per gallon of rock and for sand. For a beginner I would not recommend a deep sand bed go with no more than 1.5in of sand or less.
To make things cheaper order dry rock and dry sand. This helps in a couple ways. You get no un-wanted pests and as you buy dry rock the less the reefs in the ocean are being destroyed by people wanting it in tgis hobby. Check out reefrocks.com marcorocks.com and some ebay people sale it as well.
Equipment: your lights are going to depend on if you want coral and what types of coral. If a 30 breeder you can get a dimmable led
light on ebay for about 100 bucks. This will give you a nice look and gives you away to have a wide variety of intense lighting. So you want softies lower the leds all the way you want sps
higher the intensity. I would get a skimmer theres a lot out there. Stay away from ebay on the skimmers unless someone is getting rid of a used one thats a good brand. Octopus, aquamaxx, theres a lot of them. I have reef dynamics I love the thing I would buy another. Are a little pricy but I have a 125 a little bigger than yours if you get 40 or below. So you skimmer will be cheaper.
I wouldnt run a hob
filter. If you have a sump throw your carbon in a filter sock and there you go. I do like filter socks you do have to change them out every three days. I wash mine so I reuse them. Bulk reef supply sales them and there filter socks for a good price. You will need a power head a heater and a return pump.
The powerhead I have the jebao wp-40 they do have a jebao wp-25 for smaller tanks. Check those out ebay. Great price for what they do compared to others.
There is so much you can do to a saltwer tank the best thing is to research everything. Thats what I did. It helps. Also asking too.
To save money build your own stand unless your get it off of craigslist with the tank.
You will need a hydrometer or refractometer(prefered) amazon. A saltwater test kit. I hope I said everything. If I forgot something just say so.