Each of the light fixtures draws about 1 amp without dimming. You can safely use #14 wire for up to 15 fixtures in a circuit, no need for #12 if the 24 lights are NOT on the same circuit.
Your total maximum current draw for all the lights will be 24 amp which will require 30 amp breaker and #10 wires throughout per the electrical code. If you have enough space on your panel split it into three 15 amp breakers and use #14 wire throughout for each circuit, it is much easier to work with #14.
I was initially planning to use 2 light switches for my 1,000 sf shop but ended up using 1 switch with a dimmer and I am very happy about that. I wired everything with 14/3 Romex. I ended up using the 3rd wire for the dimming but I had to put some extra electronics because I was missing a wire. My circuit breaker is 15 amp which is enough for 10 lights.
For the dimming wires you can use 18/2 or 16/2 wire as it is very low current. I found
this wire (link) to be cost effective for wiring.
You will need switch/dimmer that supports 1-10 volt dimming.
Ariel