The essential idea behind "Reaganomics" is that less regulation will allow more competition in the market and that with lower tax rates, the rich will take their money out of tax shelters and invest it in business ventures that hire workers.
There is a good essay by Thomas Sowell called "Trickle Down Theory" and "Tax Cuts For The Rich" (amazon, pdf), which explains the difference between the bogeyman of "trickle down theory" which wasn't actually advocated by any economists and the accepted idea of "tax cuts for the rich" which is rooted in fact. He looks at four different presidencies and shows that a higher tax rate does not necessarily mean higher tax revenue, and that by cutting taxes, in certain situations, you can simultaneously increase government revenue and economic productivity.
Your post is a little nonspecific so I'm not entirely sure if that's what you were looking for.
The real theory people use to justify tax cuts is based upon the Laffer Curve, which says that max revenue lies somewhere in the middle of 0% tax rate and 100% tax rate, meaning that if tax rates are too high, we're losing out on tax revenue and we can get more taxes by lowering rates, not just on the rich, but everybody. JFK did this successfully, but when conservatives try to do it, it's called "trickle down economics" and misrepresented.
Trickle Down Theory and Tax Cuts for the Rich https://www.amazon.com/dp/0817916156/ref=cm_sw_r_awdo_navT_a_RA4ZZQ17H320SF2D4N3Y
https://en.wikipedia.org/wiki/Thomas_Sowell
“Thomas Sowell is an American economist, social theorist, and senior fellow at Stanford University's Hoover Institution. “
Does this work?
145455690| > United States Anonymous (ID: g4yLg5PK)
>>145451843 Short read that may help you understand the situation better. https://www.amazon.com/Trickle-Down-Theory-Cuts-Rich/dp/0817916156