The ones you should put on are the ones YOU need or use. No one can tell you what to put on your ipad. Research the individual apps to see what they do, and guess what? If you install an app, and you don't like it, you can UNinstall it.
Best way to learn is by trying them. There are also dozens of other threads about suggested apps, suggest you read those as well, since you essentially want to start another one.
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