This works well for little stuff:

https://www.amazon.com/gp/product/B07CJKP1NF

Jameco sells a larger-gauge version:

https://www.jameco.com/z/JMS9313-01G-Jameco-ValuePro-22-AWG-6-Color-Solid-Tinned-Copper-Hook-Up-Wire-25-Foot_2153705.html

...and a much larger-gauge version:

https://www.jameco.com/z/822-2--Jameco-ValuePro-18-AWG-Red-Stranded-Tinned-Copper-Hook-Up-Wire-100-Feet-UL1007-UL1569_125736.html

...but given that this is for electronics... most of what you'll want will probably be around the 22AWG to 24AWG size range... with some forays down to 28AWG for things like digital connections.