Frank's lab apron is a great project for a beginner sewer. Very simple tunic open in the back - no darts, no zippers, no buttons. The collar has a slight "funnel" shape to it, and it looks like the facing was applied to the inside and stitched down on the outside.
There is a rectangular strip of fabric running across the front of the tunic at his natural waistline - a tie runs through it, crosses in back, then ties in front. There are also ties at the back of his collar and the middle of his back.
The sleeves have ties on the inside, attached somewhere around the bicep - they are just left dangling. You don't need to put any cuffs on the sleeves since they are rolled up - just finish the edges with a rolled hem.
I recommend a light-to-medium weight cotton fabric. If you can't find the exact shade of green, cotton will dye wonderfully (other blends may not).
Nail polish or acrylic paint works great for the blood stains. The triangle can be appliqued as an iron-on with Heat-N-Bond, or just stitched down (you know how much I love my adhesives). He's got some repaired rips on the front and back.