for the basket, you could also add gourmet teas and coffees (and accessories to go with them), various pampering items like the kinds you can find at bath and body works, etc
Not sure where you live, but here in Canada we have these jewelery shops called Peoples and Mappins, not sure if other jewelery places do this, but these guys have these cool specials of the month. Usually it's a necklace or a ring that you can get for $30-50 Cdn dollars. And these make very nice gifts, although the diamond value and the gold values aren't much, usually these gifts are worth more than $100, so it's still good value for the price! And honestly jewelery always makes a great present, especially since the girl is getting married!
or anyone have any nice engagement ideas for a big gift?
Engagement is tricky because there isn't really a change yet, and getting things for the home and stuff is not as useful cuz of storage issues. But you could do a spa certificate as someone mentioned.