Three RT's EWR-CDG will yield you close to 22,000 miles. Maybe a domestic RT ticket to get the other 3,000 or so and you will have Silver Elite, which gives you a 50% mileage bonus, access to the forward section of coach, and priority boarding and priority baggage tags.

Upgrade to Business will not happen for a Silver. Too many CO*'s and CO Plats who would get an OP upgrade before a Silver, and OP ups only occur when coach is full.