I like clean looking figures that show all the raw data, are big enough that you can read without zooming in a million times, are aligned properly and have plenty of white space. You will probably notice that as you read more papers and make more figures, your preferences get more and more precise (aka nit-picky). So, please give your mentors a break when they tell you to align your X-axis to the exact pixel and alter that shade of blue by 2%.
These articles outline tips for making a good scientific illustrations and figures.
For making scientific illustrations (and schematics):
For improving your scientific figure making skills:
For beautiful microscopy images:
Most people in my lab have gravitated to using 'R' for making figures. Learning R is a bit of a pain, but many of my mentees mention that DataCamp (https://www.datacamp.com/) has been helpful for them. This website: https://www.r-graph-gallery.com/ has everything about how to make the prettiest figures using ggplot2 in R. And this website: http://r-statistics.co/Top50-Ggplot2-Visualizations-MasterList-R-Code.html#Scatterplot has lots of great visualizations of what is possible for plotting your data using ggplot2.