Quoting Spreadsheet - Microsoft excel

We have a quoting spreadsheet created in-house. This system works reasonably well but very clunky and would like it smoother. We would like to streamline the data entry to the one page, all information can be fed into this page and then run through all connecting cells on each page. Is it easier to use drop down boxes to tick what items we want to input to help with the summary page (as below) We want to then create a summary page which only shows each item used on each page - still in each section but showing materials, hours and machinery. This page will be used as our job costing page so we need the information entered into the spreadsheet as quoted and a column next to it as actual so we can determine profit and loss on each item. Once the spreadsheet is completed we want it to be able to produce a adjustable gantt chart for the timeline of works allowed for in the quote.