The pokemon that are exclusive to ruby are seedot,nuzleaf,shiftry,mawile,zangoose,solrock,latios and groudon. Here are some tips to help you on your game:

At odale town if you buy 10 objects at once you will get a free prize.

after you get SURF, come back to route 111 and surf across the small lake here to acquire an HP Up.

to get the last few items inside mountian pyre, drop down the hole on the very top floor, and you can pick them up on your way down. After the first drop, take the bottom-right drop to get the last item.

If you go down to the cabins on the abandoned ship, that are onlyaccessible with DIVE, you'll initally find them locked. Look carefully when each room. When you spot a sparkle on the ground , search there to find the keys you need to fully explore. The key to Room 2 is harder to find because you won't see the sparkle-after you enter Room 6, go left into Room 5 and search carefully. You'll find it about midway through the room.