You’re looking to produce an impressive report or set of charts from Excel, but don’t forget that a good-looking chart or report is meaningless if you haven’t used the right data or calculations.
Before that final step, where looks are important, the most important thing is to lay the data out well, and ensure that the logic is clear and repeatable.
Have you included all the rows? (missing out rows is a simple mistake to make, but can produce wildly different results).
Has the information been formatted consistently (for example, some percentages might appear as 12% (in which case Excel stores it internally as 0.12), while others might appear as 12 in a percentage column (and Excel will store it 12, 100 times bigger than you mean it to be).
Can you trace your working easily through the spreadsheet? (someone verifying your results needs to be able to do this. That someone may even be you after several months.
This is also important if you wish to develop the spreadsheet further or debug it).
Do those stripy tables add anything to the understanding of the data? (if you’ve made good use of Conditional Formatting then stripes will just be confusing.
Don’t merge cells except in the final output, where you know no calculations will be performed on the cells.
It’s best to leave the prettifying until the final stages, other you can waste a lot of time to find that something needs changing again.