[john hall]

A good quality 3/8 drill (ordinary, not a high production grade/design) in a machine shop in a rigid setup will run at 900 RPM's with plenty of coolant. In a CNC mill with flood coolant you could push it up to about 1050. On a manual mill probably more like 700. I assume you are on a drill press or hand drill, I'd keep it at around 450-600 and use a heavy oil--at least motor oil. WD-40 is too light for much of anything, maybe aluminum but it will still get you in trouble there. If your chips are blue, you are running too fast. Carbide can tolerate blue chips, HSS tools can't.

If you must buy more drills to finish the project, try to get something made in the USA if it is available local without paying a fortune. I would stay away from China and certainly no crap from India.

You shouldn't need a pilot hole, at least we wouldn't even think about it at work unless we are using a hand drill. I assume the tool is turning reasonable true in the chuck? That could cause some serious premature wear on the corners. As was suggested, try re-sharpening the drill as soon as it becomes dull. The best way to do that if no one is around to teach you is to watch a couple videos and then start grinding one that is burnt up until it looks just like a new one. Keep the angles the same, both the point and the clearance angles. Too little/no clearance and it won't cut at all. Too much and it will try to pull itself into the work causing the drill to stall or the point to break.

If you have time, order some drill bits from MSC. You don't need anything fancy, a good set of no-name made in USA will work fine, jobber length would be best for around the house. Unfinished or black oxide will work just fine, no need to pay extra for TIN coatings (gold).Trust me on this one, I purchase all the tooling for a 25 man machine shop and we just use mid grade tooling unless I have need of something more high performance for a large CNC run. FWIW, most of what we work with is tool steel.