Dosing pumps add things in very small quantities, like 1ml per minute. With one and a timer you can spread out the addition of key elements like calcium and alkalinity. Thus avoiding spikes. Be fore you can benefit from using them you need to have a feel for what the consumption level of your tank is. So manually adding for awhile, while conducting tests, is the best way to find out. The dosing pumps are very nice though once you get them tuned in to your tank's needs.
Just adding once a day gets old after awhile. And with a dosing pump/timer/controller you get to spread that out over the day. Stability is key in reefs. A lot of people will add calcium during the day and alk at night. pH drops at night when the lights go out and alk additive tends to drive pH up. So, end result is you have have less variation in pH.
If I were you I'd manually monitor and add calc and alk as needed and then considering dosing pumps to automate the process down the road a ways.