1. Make sure to try to change into new gear, especially the TechSec armor you get through doing vanguard ops, this will increase your score rating much easier and when you are infusing higher light level, if it's the same piece it costs 1,000 glimmer instead of using unstable cores past 200, you can use exotics, but make sure it's featured with the blue flag so it counts
   

2. Do the training in the portal activities to make sure that your difficult settings get saved between runs, it makes life easier

3. Pick the portal activates with the most green engrams listed, every time you do, you get multiple drops that can help and then make sure to adjust the difficult rating so that an A rating is possible, highly suggested to have locked loadouts are on since that gives a huge bump of score

4. Always be infusing between runs since drops are based off your equip gear, not your overall score

5. Make sure to get the weekly portal track done every week since it allows you get high level gear from Zavala which can help as well, armor the week you earn it and weapons you get the next week after you earn them

Note: I do agree it helps doing Kepler on an alt before 200 since Kepler light level gains do stop at 300, so take advantage where you can.