I see that you cut your roster down to 13 like the tutorial suggests. However, I think a better strategy is to take advantage of the salary floor not applying to new teams. In each division there is a minimum salary your team is required to pay, even if your salaries are below the minimum. Because it doesn't apply to new teams, you can shrink your roster down to just the necessary players until it does apply. If I had your team, I would keep your two 18 year old big men with all-star/perennial all-star potential and the player with the lowest salary. I would then sell or fire the rest of the team. The reason for this is you need to dress a minimum of three players in order to receive training minutes. The two 18 year olds should be your trainees and the one extra is to meet the minimum requirement of 3. This is the most money you can make as a new manager. Remember that with this approach you have to switch the tranees' positions every game so they receive minutes at the position you are training. For example, you play one big guy at center, the other at power forward, and the third player at one of the other positions. Let's say you are training Inside Offense at the Center position. After playing your first game of the week, you swap your big men's positions for the next game. This way both receive 48 minutes (max amount of training minutes) at center. Also, I'd recommend a level 4 (advanced) trainer on your staff to start.
You can also consider selling the two guys I mentioned above. They can sell for 100-200k each. Then you can either select two 18 year olds from your roster with star potential or purchase two 18 year olds with star potential to train. The reason for this is a level 4 trainer with a good salary is the best you can afford at the moment. Your best 18 year old trainees won't reach their potential with a level 4, but a player with star potential will.
If you decide to use this method, remember to constantly check your economy page to see whether or not the salary floor applies to you. Once it does, spend you accumulated money on good players to play alongside your trainees. I think anyone can become a threat after one or two seasons easily with this method.