That depends. $1 million is the goal for a lot of people. Starting with 100K means you’re closer to it than most.
Index funds have a solid history of high ROI, somewhere between 7-10%, but that can take quite a while. So, hypothetically, you invest all of your 100K into an index fund that averages 7-10%. Your money accumulates interest which is reinvested into the index fund. You’re building more wealth through the interest compounding in this way, but it will still take around 10-15 years to reach $1 million. That might seem slow, but it would likely take a lot longer without your 100K to jumpstart the process.