(a) After you get Highwind (Disc #2), go to Chocobo's Farm and borrow stalls (10.000 gil each) as many as you want. If you have a patience, borrow 4. If you don't have a patience, borrow 6.
(b) Leave and get on the airship, fly to the northern continent and land near the lone house surrounded by grass. Equip one character with a Steal (yellow) materia and keep walking around on the grass until you fight a large red reptile (Brachosaur?) Try to steal from him until you get a Karabu nut. Either run away or beat him, then repeat this process three times so that you have three Karabu nuts. You can also get this item from the same enemy if you go to the tip of the penninsula near the excavator's village on the Northern Continent where the dark grass is.
By the way, you have....