I actually feel a little bad for Shakti and all the younger sons in general. In those days, the oldest son was given everything, the best training, the most love, the inheritance, the love of all people, etc. It's pretty normal to feel jealous. And the way Udai treated his mother disrespectfully would hurt anyone. In some senses, he just wants to be given a chance to shine, a chance to be appreciated. With the way Shakti has been portrayed, I think if Shakti was appreciated as much as Pratap and continually acknowledged for his good things, and his mother not treated so badly, he wouldn't be so resentful. After all, kids don't grow up evil and selfish, they are moulded into that.
And regarding Pratap and his Guru ji, sometimes I feel as if the Guru ji is unnecessarily strict with Pratap. I mean he's definitely mellowed down a lot since the beginning, but still. But I guess it's good that it motivates Pratap.
On another note, I wonder if this show will take a leap in the near future because Pratap was 20+ when his dad died and made his brother the crown prince. I'm actually very curious as to how the show progresses :)