tbh marines aren't really your best bet for a noob friendly army! especially ppl coming from 40k who think marines shoot at everything....

also they are an air-assault/drop list at heart, which can be very difficult for a new player to get their head round.... when you get the hang of marines, they can be quite forgiving, but that's not really the case for a new player, this can definitely lead to frustration, not something you particularly want if you're trying to attract new players to the game!
I think something like the following would be your best option:
tacticals w/supcom, hunter and razorback
tacticals w/hunter and razorback
devastators
scouts w/razorback
scouts w/razorback
scouts
speeders
terminators w/chaplain
thunderhawk
warhound
warhound
tbolts
it has lots of ground formations, the tacticals, scouts and warhounds can work in a mutually supporting manner in engagements, while the terminators and thunderhawk give you a deep strike capability and can either pick off lone warhounds or the like, or go screaming in to the opposing BTS with devs/tacticals in support fire range
for the extras I'd suggest a second thawk and terminator formation, then probably some predator annihilators, land raiders, bikes and vindicators, mostly to try out other unit types and playstyles