So I'm level 20 and haven't finished the campaign.
Are Strikes and all other activities locked until I beat the last mission?
Also, what's the quickest route to max light level?
Got my first cbaracter to 284 nearly 285 in about 30 hours of play time. Here's my mehod:
Always decrypt legendary and exotic engrams right away. They dont increase in light when you do so if you dont use them they become worthless for light gain.
DO NOT do milestones until you are over 265. They are the best way apart from Nightfall to get gear over 270.
Get to around 250 from blue drops from public events and any engrams you get along the way. Stockpile all the faction rewards turnins during this time.
Omce 250 give or take, start dumping your faction rewards turnins one at a time. Check the gear you get against your current gear and wear it if its higher. If your curre t gear DOES have a +5 mod on it and the new gear DOES NOT, infuse the new gear into the current gear to get the highest light possible. This should get you to 265 easily if you stockpiled faction rewards. Try to make sure your energy weapon and power weapon arent exotic due to next step.
If you got any +5 purple weapon/armor mods while turning in faction rewards, put them on any gear slots that dont have one if possible.
Once 265, do your first exotic primary weapon quest. That will bump you to 267 or higher assuming you have a few 270 pieces already (265 gear with a +5 mod).
NOW do all the milestones. Again, only turn in one at a time and check the rewards against your current gear, making sure to maximize based on any pieces that have the +5 mods. Make sure to join a clan for the clan milestone. Also do a 2nr exotic weapon quest after 1-2 milestones if you didnt get a higher light primary than the 1st exotic.
SAVE your favorite exotic quest for last. I waited to get my mida muti tool until I hit 283 light and it dropped at 293. That is what brough me to the upper half of 284 (and allows me to USE my trusty mida).
Doing this I was able to get to 284, two points shy of 285, on my first character without creating alts to re-do nightfall and whatnot.
Hope this helps someone.