First Reef tank, need some advice

skimmer generally goes into the 1st compartment. As far as your pump you want it to match the output of the overflow. Reactors are nice, not something you have to have off the bat, if moneys not an issue sure but if it is focus on quality lighting, skimmer, rodi for now and leave room for reactors in the future.

Can do skimmer in the return. What are the dimensions of the tank? Budget for the lighting? IIRC most 58's are kinda tall so I'd lean toward halides.

Skimmer typically goes in the compartment where the drain from the display is. Skimmers are mechanical filtration so placing them where waste enters the sump is best. Placing the skimmer in the return area will only work if you have a very good ATO (auto top off) to keep the water level at a constant height in that section (and the appropriate height for your particular skimmer).

Here is a video off of Aqueon's website sheong the skimmer in the return section but what they dont tell you is that evaporation needs to be accounted for and that the water height in the return chamber may need to be adjusted to match skimmer specifications. I'm not sure if the height of the baffle that separates the 2nd and 3rd chanbers is adjustible. If not, you will need to get a skimmer that doesn't require more water height that what that baffle allows for.

http://www.aqueonproducts.com/education/videos/index.php?v=qYj7PQzl4cY

4+ bulb T5, halide(s) or good LEDs will light that tank just fine and allow you to keep most everything.

$200 is a bit low for any quality lighting plus the bulbs, may need to ask the wife to bump the budget up another $100 or so, or go with my policy easier to ask forgiveness then permission

$200 could score you a good used t5 setup or a halide pendent and ballast though. DIY 4 bulb T5HO inside the canopy can be done on $200 budget but your looking at another $100 on bulbs. A good DIY LED probably close to the same as t5's.

3-4"+ for DSB. With the retro go with good individual reflectors, as 4 bulbs is the bare minimum I'd run on a tank that size you don't want to skimp on the lighting, perhaps even consider adding 2 more bulbs some time down the road if you start getting into SPS.