The bearings you need to think about for casting are the bearings that the spool axle ride on. Figure out the size of those, order full ceramics off ebay, and replace the stock bearings. They won't fix a dumpster fire, but they will do wonders for any mid-range reel and up.
Ceramics are super light and they take very little energy to get them going so you can use really light baits. They also don't rust so you can run them bone dry which helps because they grease/oil isn't fighting the bearing's momentum.
Thay also sound cool like glass packs in a '93 Mustang.