"Best", "budget", and "all systems" are a three-way contradiction.
When it was me, I bought used Snap-On professional-grade scan tools from sellers on eBay. Pawn shops, Craigslist, etc. are also viable options.
Two decades ago, I bought an MTG2500 and eventually software cartridges up to 6.2 for '2005 back to '81 1/2, and which worked fairly well for everything except auto-bleeding the ABS on my '97 K2500. When the '2500 died, I replaced it with a Snappy Solus Pro with 8.2 software, which also wouldn't auto-bleed my '97. I later found out that 14.2 software WILL auto-bleed my '97. I've heard that 9.x and up software will also auto-bleed the '97.
I have access to all the ABS stuff EXCEPT auto-bleed with the 6.2 and 8.2 software.
Works with the instrument cluster on my '03 Trailblazer, air bags, engine, trans, etc.
I'd rather have a used professionl-grade scan tool than a new consumer-grade unit--if the used tool has software that will communicate with the newest vehicles I intend to use it with.
There are competing products from other brands, newer Snappy products, and lower-cost, consumer-grade stuff including software + dongle + smartphone; software + connector + laptop computer, and so forth. I have zero experience with any of that, other than reading forum posts about how they aren't providing info on various systems and need extra-cost options and/or additional attention/fussing.