Hey fren, thanks for your comment.
The minion that gives stats to another card can target itself because the "trigger time" reads "When this minion enters the battlefield, put a +1/+1 counter on target minion" which means the minion has to successfully enter the battlefield for it to trigger, and in turn, the minion itself is a valid target by the time you decide targets for its ability. At least that's the logic behind it.
It seems you played as the Warrior which is the most "beginner-friendly" class, so the cards and effects its starting deck has, are quite simple. I recommend you give the Trickster or the Archeologist a try if you want a more complex starting deck! Also, some combinations of Equipment pieces make for quite interesting and explosive decks.
Regarding the AI, yeah, it's all made by me without any sort of learning algorithm or advanced things like that, so it behaves sub-optimally in some situations.
I hope you get the other classes a try and let me know if you need help with unlocking anything and whatnot.
Cheers!