Push the main story quest line. You get boatloads of free gear from just doing the story quests. Make sure you are choosing the fending accessories (the vit ones). If you do that you will have all the HP you need.

Use tomes to supliment your lowest ilvl pieces.

After ALL that gear if you are somehow still behind then you buy gear. But you really shouldn't need to. Just do more main story quest and get your free chests of higher level gear.