For creating a league playable in career mode, Rather than using a random id use a id from Magical team list id's. If you are creating a league for a UEFA nations, than use any id of a UEFA nation from the magical team list. Its actually works. Mostly all the UEFA nations id's are present the list.

Here is the screenshot of israel league

But if you are creating a league for other confideration, than it is difficult. For example , only few AFC nations id's present in the magical team list.

For example , if you want to create a league for india. Now what ypu have to do is very simple. Use Iran league id and create leagues and teams.select iran as a nation fot your league not India. Create schedule and dont forget to create a tournament. Than follow the tutorial here. Here every where the nation name should be iran not India. Swap the names and flag pics of the two nations. Now you will see your league working correctly in career mode. But the leagues will be using iran's map for scouting network. Thats the one of thr bug you will encounter during your game play..