What build should I do for X distance?

In general, you shouldn’t have more than two types of cards in your URA deck (Friends aside; you can replace a Speed with Tazuna/Aoi in these). In such a low strength scenario, it’s better to stay focused. It’s also very hard to use Wit cards in URA and make competitive umas, unless you’re whaling every card. Save those for later.

These are made with PvP in mind. Winning Career is pretty simple with decent cards. The enemy umas aren’t very strong, and you have a secret +400 All Stats boost which makes Stamina much less important during training. In terms of importance with these goals, it’s Stamina > Speed > Power > Wit > Guts, for every distance. Stamina is the most important stat, but it has a hard cap on each distance after which it does nothing. When you’re far below that cap, getting more Stamina is better than more Speed.

Disclaimer: These builds are for the URA Scenario specifically. In the future, with more powerful scenarios, Wit cards are used everywhere, Guts cards have their times to shine, and in MANT, the types of the cards don't even matter, only their race bonus. Things will change as the game goes on. Don't destroy your Wit and Guts cards just because they're not shown here yet.

Sprint Inherit Wit and some Stamina. Target: 1200/500/1200/300/500 Sprint is the first distance you can start trying Wit cards in. If you have a +63 Power parent of your own, you can inherit full power and try 4 Speed 2 Wit for Team Trials, but raising the Stamina can be a bit hard. If you can’t get 500 Stamina 900 Power, stick with Speed/Power.

Mile / Dirt Inherit Stamina. Target: 1200/800/900/300/400, or 1200/600/1000/300/400 + 1 Golden Recovery Skill You can also use a Stamina card instead and inherit Power, if you lack any good Power cards.

Medium Inherit Power. Target: 1200/900/800/300/400 + Swinging Maestro A full Stamina inherit along with the Vodka power card for a recovery might also work.

Long Inherit Power. Target: 900/1200/600/400/400 + 2-3 Golden Recovery Skills *Note: Iron Will (鋼の意志) doesn’t count as a Golden Recovery Skill. Don’t take it. Adrenaline Rush (from the Rice welfare) also does nothing on Global currently. The Mejiro McQueen card you get from the story is very useful here.

That may seem extreme, but I can’t stress enough, Stamina is more important than Speed. 1200 Speed 500 Stamina is 3 seconds (~30 lengths) slower than 500 Speed 1200 Stamina on Tennosho Spring (3200m). You lose so much speed when out of stamina. You can win Career with less, but your performance in PvP will be much worse. See Stamina vs Speed.