Played about 4 hours Tuesday and reached Level 1, 1067/1200 on the way to level two. If you are new to IB here are a couple of tips taken from Bungie’s web site.
Bring your fully upgraded weapons. Level advantages are enabled.
Bring your defense up if you can. Level advantages are enabled.
Purchase the Boon from Saladin for one mote of light. Increases your event standing and the gains are increased each day of the event. It lasts 12 hours, then buy another one. It sits on your gear screen where the nightfall symbol is if you need to check how long you have left on it.
Buy and wear the IB emblem ASAP (requires rank 1), it gives a 10% boost to reputation gains. Then buy the Million Million shader (Rank 2), stacks another 10% boost. If you get to rank four you can get the class item to stack another 10%. If you are like me, you may already have these from a previous IB event. Just remember to get it from your other character and equip it.