A lot of people are telling you to farm for gear post PT1 but you have to remember that a lot of good legendary gear is going to be underleveled. For example, going back and farming a Hornet will net you a level 4 at best (I think). The one boss you can definitely farm is the last boss for the story as those drops will be around level 30. Make sure your gear is at or close to your level, regardless of what it is, before you start PT2. You don't need legendary gear, just stuff you feel comfortable using. I'd also get used to using slag through your second go around since it's not that important in the first playthrough and is practically a necessity in UVHM and beyond.

PT2 will take you from around level 30 to around level 50. You can farm for gear in this playthrough but the same issue from PT1 exists until you finish your second playthrough. At the end of PT2, the entire game scales up to level 50 and any experience from killing enemies is greatly reduced. At that point, you can farm any enemy for a chance at a level 50 variant to take with you into UVHM. If you want to farm quest rewards, you have to hold off from accepting that quest until after you finish. Then, the reward for that quest will also scale to 50. It's a good idea to farm at this time for stuff for UVHM. It's important not to level up too much during this time because UVHM scales with you. You don't want to be using underleveled gear in UVHM.

Because UVHM scales with you, you can farm at any point to your heart's content during this playthrough. If you want a quest reward at 72, make sure to not accept the quest until you've hit 72.

Lastly, don't forget about Golden Keys!!! There are a TON of active SHiFT codes that will net you at or around 100 keys. If you really feel that having purple gear all the time is going to make it easier for you, that's your best bet. Gear from keys will always be at your level.

Hope this helps!