Congrats! They will definately grow with you if you treat GE well.
Congrats! GE cards have been great for my uti.
The Old Navy card is actually really useful beyond the fact that it's a GE card if you shop there regularly and always pay the card off. It's not quite as good for discounts as a Kohl's Card is in their store, but the Old Navy rewards program is pretty decent.
One thing to note is that for the most part the Gap and Banana Republic cards are almost identical to the Old Navy card. For whatever reason, the ON rewards program is slightly more favorable, since you get rewards in $5 increments instead of $10. (So instead of needing to spend $200 to get a $10 card, you can spend $100 and get a $5 reward card; and if you do spend $200 you get two $5 cards.) In any case, you can still use the ON rewards in other Gap company stores, so there's really no reason to have the other cards if you plan on actually using the rewards program.
That said, the Old Navy Visa isn't quite as helpful. You can earn 1% with the Old Navy Visa if you use it outside Gap stores, but you can earn that much or better with many other cards, some of which allow you to use the rewards for cash back or purchases other than just clothes. I've only ever bought one non-Gap thing on the Old Navy Visa and it was only because the first time you use it for a non-Gap purchase you get a $30 reward card.