Sust should be shot EOD for most stable blood level (actually every day for optimal). E3D is the least frequent interval that will still keep relatively even blood level.
So if your sust is 250mg/ml concentration:
EOD: 0.6ml (150mg) = 525mg/w
E3D: 0.9ml (225mg) = 525mg/w
There are a bunch of online providers at low cost (example: http://www.gpzservices.com/).
I like to get 1ml syringes with no needle separately and a variety of needles to attach as required.
I use 22 gauge (22G) 1.5" to draw from vial and then switch to a fresh 25G to inject. The long length is only really needed when getting last bit from bottom of vial or reconstituting HCG.
1.5" for glutes & ventro glutes (I actually get away with 1" for these sites)
5/8" or 1/2" or 1" for quads, delts & pecs depending on leanness.
I use 50CC insulin syringes for HCG and also for small doses of oil as during a stasis/taper PCT. I draw and inject with the same needle in that case.