Step 1 - Play through main story
Your main goal during this first step is to play through the main story, while keeping a few things in check to make things easier for you in the long run. Along the way, you want to do as many Substories as possible, since not only will you get ingredients and healing items, but you will also gain levels with your characters. Note that you only need to complete 10 Substories in order to get the Do-Gooder trophy/achievement, so you don’t necessarily need to do them all. The reason you want to do them as you go along in the main story is that the majority of the Substories become missable, as there is usually only a small window in which they are available.
Another thing you might want to watch out for is instant victories, of which you need 50 for Can’t Touch This. At some points during the main story, you might notice that the random encounters are a lower level than you. If they are at least 5 levels lower, then you can use the boost while flying to run into them and instantly win the battle without actually having to do the fight. This is important to do during the main story, as most of the random encounters will scale to your level after the story is complete, making it much more challenging to do.
While flying around and doing things in between main story missions, you will also want to keep a lookout for NPCs who are talking about “recipes.” These aren’t normal recipes, but instead for full-course meals, of which you need to make five different ones for another trophy/achievement. Once you hit Intermission 2, you will unlock the Dragon Balls. You need to summon Shenron a total of 10 times for a trophy/achievement and you want to work on this while doing the main story, since you have to wait 20 minutes before you can use the Dragon Balls again. Lastly, while it isn’t important, do check up on Master Roshi from time to time to hand in his Turtle School training challenges.
Step 2 - Villainous Enemies
While you could work on this during the main story, it doesn’t matter as much, since nothing will change after you complete the main story. These are the Villainous Enemies, which are stronger than normal enemies that appear in certain areas as you progress in the main story. Once you clear a set of Villainous Enemies, some stronger ones appear and when you’re done with those, one final Villanous Enemy will show up. Defeat this one and you’re done with that region. While you only need to defeat 30 Villainous Enemies for a trophy/achievement, you will be required to defeat all of them to spawn Mira.
Step 3 - Cleaning Up
The final step for the platinum trophy/all achievements is to get the rest of the trophies/achievements. This includes summoning Shenron the rest of the 10 times you need, Training Grounds, the training room in Capsule Corp, and a bunch more.