Two approaches apply here.
(1) More cost up front, MUCH cheaper in the long run.
Buy proper, albeit expensive, equipment up front and avoid killing thousands in fish/corals.
(2) Low up front cost, MUCH more expensive in the long run.
Buy low end equipment and have an unstable ecosystem that cant support the life that you are trying to host.
I am not saying that you need a controller but looking at a key piece of equipment such as a protein skimmer, using a SC skimmer to save ~100.00 vs buying an SWC/SRO etc means that you will not be skimming effectively which means that your water quality will degrade over a short period of time and you will have algae breakouts as well as livestock deaths.
You will be asking why am I having problems while thinking "I have a protein skimmer" when in reality, you really dont. The money that you lost on your fish will quickly add up to the ~100.00 that you "saved" by getting the SC skimmer and you will still need to buy a proper skimmer so you are out the money for the livestock and the cost of the SC and you will still have to buy a proper skimmer meaning that now your skimmer will end up costing +~100.00 (dead livestock) + 100.00 (SC) + 250.00 (proper skimmer) = $450.00 vs buying the 250.00 skimmer in the fist place and avoid killing livestock in the process.
The same logic applies to any key piece of life support. Buy cheap, buy twice. Do yourself a favor and buy quality the first time. You can get a used, but good quality skimmer, in the for sale forum for ~250.00 shipped.
I dont think you need a controller at this point, especially since they cant monitor nitrates/nitrites/calcium/alk/phosphate but I would watch Ammonia and pH at your stage of the game (no corals) as those are your biggest threats.
If you dont know what dosing pumps are then I strongly discourage you from getting into corals (especially SPS) until you know more. You dont need dosing pumps, per say, buy without them you will need to test / manually dose VERY often to avoid killing corals as they are very sensitive to ALK swings.
Good luck.