You definitely came to the right place to ask!
1. To just add a complete set instead of adding the cards individually, go to the set's page, then Collection Summary, and you'll see a green button under "Sets" that says "+ Add". Do that and you're done.
2. To add large consecutive groups of cards at once, go to the same Collection Summary page above, then "Add / Update". Find the first card in your run of consecutive numbers, then click the little down arrow between the check box and the card number link. Click "Add from here" and you'll go to a new page where you can click "To Here" next to the last card in the run. (To make that easier, first, I'd recommend going to your profile, then "Edit Profile". Scroll way down and you'll see an option that says "Rows to show on checklist page?" and max it out at 1000.)
3. Another method instead of #2 is to add all of the cards in a set to your collection and then just remove the few you don't have.
