Are you just running leonArdo or also other programs? 15 pairs shouldn't be a problem with your setup though.
I have many other programs running. BURST miner (minuscule resource usage, not noticeable outside of its deadline cycling), Firefox ~8 tabs (+YouTube), a wallet or two. I try not to do anything intensive on my Windows machine (I use a Mac for work).
Looking at Windows' built-in Resource Monitor, leonArdo never goes above ~25% CPU [when in the background] and ~35% CPU [when actively using] with around 20-30 threads going, and a memory usage of ~800MB at any given time. I currently have 14 coin pairs actively trading using the mArgin maker. It's really not that big of a deal right now

just wondering -- if I get really serious with leonArdo, if I should have a dedicated machine with a Ryzen or Core i7 that I do not use for anything else?