Which sources of randomness are available?
Whether you need a source of random noise depends on whether your project needs to not run repeatably. Most experiments - Monte-Carlo simulations, for example, benefit by being able to be re-run. In those cases, you need to be able to re-use the seed, and having an non-reproducible seed (and thus, experiment) is a disadvantage.

If you really need something that runs differently each time you run it, then a seed derived from user reaction time, or from some kind of electrical noise, even reading analog values from a floating input pin, should give you plenty of non-reproducibility.