Seeking Advice for better forecast

Hi there!

Hope you guys are doing well. Just wanted to reach out to get some advice on how to do a better forecast. Any advice you kindly share is greatly appreciated.

Just some context, I am new to this role, and my main task is to forecast and manage supply chain team's budget for purchasing materials. In my previous roles, I mostly work as buyer and inventory management. I also helped with some budgeting aspect but not enough to understand the full context of forecasting from FP&A perspective.

From what I understand, in general with supply chain, material's demand and cost change constantly - depending on the market and the company's want. Thus, it isn't a surprised for me to see the forecast changes (can be drastically as well). For example, if we might spend less this quarter as there is less material to purchase; but we might spend more next quarter as we need more materials.

My current approach is to follow the current planning to purchase materials and revise the budget accordingly to this change. However, this is not the best approach as my teammate is confused on why the sudden change. So, what should I have done better for more accurate forecast? Or how should I explain my finding better?

In addition, some technical challenge I have is inconsistent dataset and missing data. So, I just try my best to clean and fill in the gap as well as I can.

Sorry for the long post and thank you in advance!