Integrated circuit design is a vast field with many different areas of expertise. Given your goal, your best bet is to buy an FPGA development board and learn

Integrated circuit design is a vast field with many different areas of expertise. Given your goal, your best bet is to buy an FPGA development board and learn an HDL (Verilog or VHDL), and start experimenting. When you to deeper in the field and more over to ASICs, then you would have to learn the details of synthesis, placement, routing, DFT (design for test) and a whole bunch of other details, which usually exceeds the willpower of a hobbyist :-) And then if you want to really go all the way into the latest and fastest transistor nodes, then you go into custom circuit design and custom gate layout, which is not fun at all.