Should I start investing with a lump sum or monthly contributions?

Monthly contributions reduce timing risk
Investing a fixed amount monthly (dollar-cost averaging) smooths out the impact of market ups and downs. You buy fewer shares when prices are high and more when they're low. This removes the pressure to time a one-time investment perfectly and suits most people starting out.
Lump sums capitalize on history
Historically, investing a lump sum all at once captures market growth immediately. However, you risk buying right before a downturn. Lump sums work better if you've already been saving and the money isn't time-sensitive.
Practical approach
If you have extra cash and a long timeline (10+ years), a lump sum is defensible. If you receive regular income and can't save much at once, monthly contributions are more realistic. Many investors split the difference: invest what you have now, then add monthly going forward.