extra 20 gauge wire is useful.
water-proof connectors are great --
>> 3-conductor for the connections of smart strings to the SSC
>> 4-conductor for the connections of dumb strings to your favorite DSC, MR16, or whatever controller
>> 4-conductor can also be useful as a waterproof alternative to cat5 to your SSC from the hub, replace one end of the cat5 cable with the waterproof connector and don't bother with SSC pigtails.
I like the 3-channel DMX controllers from Ray. They are water-proof, and they work nicely for dumb strings (ribbons, rectangles, etc.)
I have a DMX "decoder" for my specific smart string chip... it is useful to compare behavior from RJ's SSC to a different implementation of power/data signals.
The 27-channel DMX controllers are a good alternative to the 16-channel MR-16s.
Ray has DMX testers, but I haven't tried them. I understand they work well.
Of course there is a huge variety of Smart Strings options (flex ribbon, rigid, rectangles, squares, and pixels -- I use many of them for different applications). There are also similar dumb string choices as well.
If you intend to cut and splice flex strip there are corner connectors. (haven't used them) and connectors to join the end of the ribbon to your cabling (I got the wrong size). so, figure out what you want, and ask Ray to verify the sizes.
How big is your budget??