His most important achievement was back-channeling a deal with Saudi Arabia (through HW Bush) that mitigated the threat posed by oil shocks and collapsed the price of oil, which brought down the USSR.
He increased military spending by increasing the size of the standing force and raising cash/non-cash benefits for active duty personnel. Military is about the only lower-middle class entitlement we have.
Tax reform and tax efficiency improvements. Social Security reform of 1983, the most recent Social Security solvency reform. Supply-side macro economic policy tools that we still use today.
Unlike other presidents, Reagan actually used the War on Drugs to combat narco-terrorism in the Americas, which at least created some moral equivalency for the persecution of drug users in the US.