How long is a piece of string ?
The right answer to this really depends on the graphics and how you put it together. If you print everything as a bitmap image (which I would not recommend), then you will need to look at the graphic and decide what is acceptable based on things like font text. Anything under about 14-16 point and you would need 300dpi, the same logic can be applied to small details.
If you are just printing disney style graphics 150-200dpi will be sufficient.
If you work smart you will keep vectors and text as that and then you can generally stick to 150-200dpi for bitmap images and all text and vectors will be printed at the same resolution as the printer is working at.
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