My opinion would be a 3" downpipe and an intercooler mod like a Dut neck, or used upgrade one
To make HP, you need air and fuel, AND it needs to easily get into the cylinders and get out as well.
Since the DP and IC will give the inlet air less restriction, this will allow a boost [and HP] increase using your current pump gas.
A turbo upgrade before the DP/IC mods will not be very effective if you have NOT increased air flow in and out of the engine.
Alky does not add octane, but allows more boost [to a point], since it will cool the incoming air to the cylinders.
To take advantage of an alky system, you still need to increase air flow in and exhaust to exit.
Your second step could be a turbo or alky system.