It depends on what type of cartridge(s) you're reloading for and for what purpose.
There's really two main types of cartridges: handgun and rifle. The manufacturers for each are often distinct. For example, Sierra is one of the premier rifle bullet makers, but they're not popular at all for handgun bullets. Vista (Federal/Speer) is at the top of the game for defensive handgun bullets, but really sort of mediocre for rifle bullets. If it has to be one manufacturer, Hornady probably covers the gamut. Then again, your purpose really determines whether you need outstanding performance from the best bullets or just sufficient performance at the lowest cost.
You are probably reloading for fun and perhaps to allow yourself to shoot more, rather than to craft for competition or personal protection the highest performance cartridges possible. With that in mind, you might not care for the highest performance bullets, but rather be looking for something you can shoot more of. For this purpose, I recommend RMR bullets. Their plated handgun bullets are very affordable and of high-quality. They also frequently have bullets of other manufacturers, sometimes pulled bullets, that are at very affordable prices in bulk. Hopefully you shoot a lot and can buy bullets by the 1000 or 2000. I also have good results with Berry's plated handgun bullets.
You may also have a different purpose for rifle cartridges in particular. Maybe a high volume isn't so important but you want good performance for hunting. I won't eat anything shot with a lead bullet. For hunting, I load Barnes monolithic bullets like the TSX and TTSX. They're too costly to shoot for general marksmanship training, but Barnes has affordable bullets in varmint calibers. For my rifle, for which Barnes does not, I use Speer TNT's. Again, Hornady would have the bases covered with Monoflex and GMX bullets for hunting, and FMJ or SX (spire point) bullets for target practice.
Generally speaking, you can substitute bullets of the same weight and similar construction (jacketed for jacketed, plated for plated, cast for cast, solid copper for solid copper) but different manufacture using the published load data so long as you use good practice to start on the low-end of the data and work up carefully looking for signs of excess pressure.
I don't recommend using data for one type of bullet, such as a plated bullet when loading another type such as jacketed (FMJ or JHP). The pressures can vary substantially. They can do so because the start pressure of bullets of different hardness vary and because bullets of the same mass but different construction can be different lengths. A 125 grain cast flat point is much shorter than a 125 grain copper monolithic hollowpoint. Since published data uses the cartridge overall length to specify how far down into the case the bullet base is set, the bullet's length very significantly affects this. Generally, plated and cast data are very close if they have similar nose shapes and styles. Also keep in mind that cast bullet data is often limited so as not to exceed something around 1100 fps because at higher velocities soft cast lead will foul the barrel. If you use data that shows the pressure, you can see it's not near the limit, but the velocity is low enough not to foul. I mention this because cast and plated bullets are typically the most affordable to shoot for handguns. If I couldn't shoot plated bullets, my ammunition expense would be 50% higher except when I could find pulled jacketed bullets or other deep discounts.