Hi.. opinions please... if you wanted an sps tank with some fish.. what 6 things would you dose? ...
First off, and most important, only dose what you need to. Every tank is different. In some cases, the best approach is to use a high quality salt and make water changes to maintain your parameter levels.
Only consider dosing if you can't maintain calcium, magnesium, or alkalinity by doing water changes.
Also consider a calcium reactor and a kalk reactor. While an expensive initial investment, they are very low cost to run. Again, only go with what you need. You might get away with just a kalk reactor or you might need both. Generally a calcium reactor is only needed on tanks with massive amounts of SPS corals.
As for other trace elements, if you can't test for it, don't dose it. You have no way of knowing if your using too much.
Don't expect dosing to make up for SW that is off on it's parameters to start with. Dosing is something to maintain your existing levels. If your newly mixed SW isn't on target, you need a better salt.
Go slow with dosing. It's almost always better to add too little than too much. Improperly used, you can turn a minor parameter problem into a real mess.