Since you're new to kegging you'll have some choices to make; When it comes to the clean/sanitize/purge part there's a few options/comfort levels: Ideally the keg will be 100% filled with Star San and then purged. You can do this with fermentation gas or CO2 from a tank. You may wish to keep one of the regulators free for 'utility' purposes such as purging and force-carbing. As to serving pressure;
IF you're going to serve all 3 kegs at the same pressure, you might as well get a 3-way manifold
https://www.brewhardware.com/product_p/co2man3_bh.htm and use 1/4" ID EVABarrier
https://www.brewhardware.com/product_p/evabarriertubing6mm55.htm to go (swaged
https://www.homebrewtalk.com/threads/eva-barrier-line-conversion.733937/page-2#post-10406957 ) from your regularor barb to a swivel-nut
https://www.brewhardware.com/product_p/fflbarb516.htm to the manifold...then you can use the MFL>Doutight adapters
https://www.brewhardware.com/product_p/pushffl.htm to whatever size gas line you want use;
https://www.brewhardware.com/category_s/1837.htm Of course we'll all encourage you to protect your beer from O2 all the way and use EVABarrier for your beer lines as well, so I'd recommend new shanks;
https://www.brewhardware.com/product_p/shanksstowerpush.htm If you want to keep your beer lines short, 37" of the 3mm ID EVABarrier is perfect for most styles.
Just wanna provide food-for-thought before you hit a 'buy' button.