I usually use 24AWG or 26AWG. I purchased some silicone-insulated hookup wire from aliexpress a while back. Really nice to use, robust, doesn't melt when you have to solder to it and is more flexible than the usual PVC insulated wire. This is now my wire of choice for use in rocketry.
Smarter Shopping, Better Living! Aliexpress.com
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Another alternative is UL1007 rated wire. This is "appliance" wire and specified by various international standards like EN61010-1. It is mechanically more robust than just a plain PVC wire, hence its designated use in consumer appliances by the relevant safety standards. We use this in our spectrometers.
Smarter Shopping, Better Living! Aliexpress.com
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The links posted are just random links found on aliexpress. Other sources can be found.
In the absence of either of those types regular stranded hookup wire is probably totally acceptable too

. Don't make it more difficult than it needs to be.
Also, if you want to fit ferrules to the ends of multistrand when it goes into terminal blocks I recommend getting something like this. Makes for a nice job.
Special Four-Mandrel Crimping Style for Square Crimp. 1pc x Crimping Plier. 200pcs x Ferrule size 0.5 mm². 200pcs x Ferrule size 0.75 mm². 300pcs x Ferrule size 1.0 mm². 250pcs x Ferrule size 1.5mm².
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