What economics theory explains changes in purchasing different types of goods? I am thinking about the first of the month. I spend more of my money on superior goods and, because of that decision, less on normal and inferior goods. Are income and substitution effects enough to explain this or not?

I am thinking about a hypothesis for why people change their types of goods given that budgets change according to pre-decisions.

I will not misguide you: this is not only a goods decision or money constraint; it is also related to the time constraint and time-involved work.

For example, an agent has a given time constraint, T, to work on his given projects over a time period, t, which requires only T-r amounts of time for the period t+1. Hence he spends the time r to do other things according to opportunity cost theory. Therefore, he spends his time working on this project only at amounts equivalent to T-r and the opportunity cost of this project decreases as time approaches t+1.

So at this point, if he is an expert at this job, everything will go smoothly but, if not, this is a false prediction and the agent has to face his false decision and survive on his present condition. The hypothesis starts here: 1. Will he increase his purchasing power (i.e., sleep less to increase the time constraint)? 2. Will he bargain with his boss to increase his time constraint? Why?
If you research "discount rates", "time preference" or similar, you'll find all sorts of stuff about seemingly inconsistent decisions, some of which can in fact be explained quite well and some of which show some ways that people can be dumb sometimes. You'll find lots of approaches to modelling comparisons involving things like someone revealing an implicit interest rate of over 100% per annum in one situation while accepting 5% as a good return in another situation. 

I wouldn't focus too much on any specific paper. Check the bibliographies and see the variety of what's out there, and maybe narrow in on a handful of most-promising conceptualizations afterwards.

As a point of contrast, you could introduce the lifetime income hypothesis of Friedman as discussed in many 1st and 2nd year textbooks.