I would say that 20 blast markers including some big ones to use as 5 BMs would be enough, you can use almost anything, many people use glass beads, some use poker chips, or pennies and there are a large variety of more 'realistic' ones, I use the old GW card ones, I've seen some really spectactular clump foliage ones, you can get metal ones and laser cut acrylic ones from litko.....
Order dice aren't required, handy, but not required, until I got mine super cheap from an ex-GW employee, I used 20mm GW bases with symbols painted on them, I used an exclamation point to mark activated units, divergent arrows to mark broken stuff, crosshairs for overwatch, and one or two marked 'reloading' 'marched' and 're-roll' to put next to the supreme commander, I *think* I still have them somewhere, you can have them if you like
