Well...usually people like to use orals to kick start a cycle while the injectables are building up stable blood levels. The hormones go to work right away but most people don't notice strength and weight increases after several weeks with long esters. The Sustanon is a mix and tbh I've never used it but I imagine it will take several weeks for you to "feel" it while the var should be felt sooner.
I have no self control so I woulda popped an anavar and injected a cc of test before I even thought about asking..lol. For me, I'd like to feel the effects right away...
It comes down to personal preference cause I think either way... at the beginning or at the end will not make a big difference. Time on will dictate your results...I don't know your experience but for me, I'd rather use what you got there and divide it (somewhat evenly) in a way where I can extend it the longest...like 16-20 weeks.