I would go with dosing until your tank has high enough consumption to justify a calcium reactor. Unless you are a gear junkie and love the challenge of setting up a new piece of equipment. I would not diy it unless you enjoy that because it might not save you that much money when you get to version 3 of your own design.
Many people really like their calcium reactors but I have never made the leap. Reactors can be expensive and hard to tune especially if you are trying to do it cheap and avoid controllers or other parts that make the reactors easier to work with.
To me, I am still dosing but it is all automatic. Mixing is not that hard to do because. I tend to mix 4 gallons at a time (2 of each Calc and Alk) and that lasts me about 2 months I have a 180 gal mixed reef. It cost me around $150 to get started and it has worked great for me for 5+years. I am not saying that I wont go to a reactor but I'm having a hard time seeing why.
Maybe someone with a calcium reactor can chime in on what they like and how much their setup cost.