You can grow the EV berries (Pomeg, Kelpsy, Qualot, Grepa, Tamato, Hondew) or use the GTL and buy them. All EV berries take 44 hours to grow. There is a berry guide, but here are the combinations for farming.
Pomeg: 1x plain bitter, 1x plain spicy, 1x very spicy
Kelpsy: 1x plain sour, 1x plain dry, 1x very dry
Qualot: 1x plain spicy, 1x plain sweet, 1x very sweet
Grepa: 1x plain sweet, 1x plain sour, 1x very sour
Tamato: 1x plain dry, 1x plain spicy, 1x very spicy
Hondew: 1x plain dry, 1x plain bitter, 1x very bitter
Here is the guide: