As for overflows, I understand you want to keep costs down. If you decide to buy one, the best one out there is from LifeReef. The reason, is they never leak and I have heard of people not losing suction for years....
I have one and it is awesome. However, I would recommend the durso attachment, otherwise it is noisy.
On other vendors, I have seen good and bad reviews. Also, some of these types of overflows, will lose prime during a power outage and even need to be reprimed, so that you have to run a pump with it, to make sure prime comes back on.
Sometimes, the LifeReef overflows are sold used and people snatch them up quickly.
Just remember, that a number of times, people have had problems with their overflows, so buying a great product from a vendor, may be easier in the long run.
PS. Please, save yourself a lot of trouble and don't plan on running a lot of flow through your return pump. That can cause micro-bubbles and be bad for your tank.