Here is a comprehensive guide explaining what to look for, how to test the game, and why seeking out "repacks" for demo content can be problematic. Understanding the RimWorld "Demo" Landscape
RimWorld is a complete, deep, and satisfying experience on its own. You can buy the base game and, if you enjoy it, add the DLCs one by one over time. This spreads out the cost and prevents you from feeling overwhelmed by all the new mechanics at once.
If you are looking for a "RimWorld demo repack," you are likely seeking a free way to test an incredibly popular simulation game. While the temptation to find a free, pre-packed version is high, the best—and safest—way to experience the depth of RimWorld is through the official, supported platform.