Board Thread:Tapped Out Help/@comment-10662082-20130610050852/@comment-26143371-20160711205314

Being behind a few levels is quiet normal. Most people accumulate XP faster than Cash.

As for what you should buy next, I'd say that's pretty much up to what you want first. There won't be new levels anymore, which means the price for the Googolplex won't be reduced like it used to be for other buildings once new levels got released. Thus you won't be able to save money by buying it later.