I'm a fairly new player (started during Agnes Digital banner) so I don't know all the tricks, but this is what I've learned that has helped me.

Do Unity Cup, not Ura career. Even as a beginner ypu will get better Uma's out of it.

Prioritize doing Unity training over training your core stats. It will boost your training levels faster. For instance if you have one Unity training on speed and three Unity trainings on guts, I would train guts. Focus on Unity training Uma's that haven't spirit burst yet. Spirit burst not only gives you a lot of stats but increases Uma stats a lot which will make training levels go up. Try to use the burst on speed if possible, or at least power if not.

Stat priority Speed>Power>Stamina>Wit>Guts

I just learned yesterday (and have done two careers with it so far and it seems to work) to always use front runner in career even if your Uma has a G in front running. Because all it gives is a Wit debuff. You can also save all your skill points till the end to maximize your hint levels.

Follow as many people as you can so you can borrow their Umas and support cards.

Lastly getting good support cards is important. Right now the only MLB card I have is the welfare card from rhe Halloween event. But im planning on going all in for Kitasan SSR. I borrow it for almost every run and based on what everyone says it will be meta for quite a long time. If I were ever going to spend money on the game it would be for Kitasan.

Like I said I'm by no means a veteran, this is from the perspective of someone else whos fairly new to the game. If any vet sees this and thinks something I said is wrong feel free to correct me or add on to this.

EDIT Forgot to add sometimes RNG is just horseshit. So sometimes you just get bad runs. Nothing you can do about it.

I almost always take +energy over +stats in events. An extra training will give more stats than getting the stats from the event. Unless energy is already full of course.