I saw a conversion chart where "supposibly" 70mg of vyvanse was suppose to equal 30mg of adderall. For myself I don't have a lot of experience with it but I would say around 80mg maybe a little less. The thread also has other suggestions.
As for the ROA I would suggest oral. The drug shouldn't work when snorted because the liver needs to break something down or something(im really high I can't remember) but I think I read some reports of people experiencing something(possibly placebo). It is also a lot of powder, that does burn quite badly when snorted. So yeah stick with oral.
It will probably take an hour or so for him to start to feel effects, and he will probably feel more focused, have more energy, and maybe a little jittery. Might have some euphoria.
I'd suggest taking two if he has no tolerance. That's almost equivalent to 30mg Adderall which is a good starting dose. Its better taking them all at once rather than re-dosing. Re-dosing amphetamines just prolongs the effects rather than increasing the high. Take them orally. Don't snort, it won't work.
As for effects, expect increased energy and concentration/focus. Possible sense of well-being and euphoria. Stimulation. May feel social.
I take it, but I find it useful as well as recreational. I am not addicted to it so I dont take too much. I find anything more than 90mg is usually not that much better since lisdexamfcoolamine has a low ceiling.
The first time I took Vyvanse I took a 60 mg cap and it sucked. I fuckin' hate that time release bullshit, I can handle Dexedrine Spansules but a really long, shitty high that doesn't let me sleep is NOT for me. Your friend should just take 2, that's (I think) equivalent to 25 mg of Adderall XR.