What you need to spend to kick-start - spend.
What you can wait and not mission critical - wait
What you can wait but is mission critical - don't wait

Need to understand the concept of trade-off - if you are very confident that people like what you are doing and you know the customers will increase in a rate that can cover your overheads, you may consider taking the risk to invest. When investment may be huge, ROI may not be appropriate, other calculation methods may be required.

So the question is not "should invest" or "should not invest", the question should be what is the method available to help you to evaluate your investment in your business.