Where you, dear angler, are the "subject".
Last time we examined your head, so now we consider your other end. What you wear on your lower reaches will depend on several considerations. Will you be wading? Will you be deeply wading? (No not deeply wailing! Save that for church.) Or will you be fishing from the bank and only the bank. In a dry summer it may be much more comfortable for the bank angler to leave the wellies behind and instead wear some outdoor boots. I know some very successful dry fly anglers who wear chest high wading stockings in all conditions, even though they do not intend to wade. They value the protection above the potential for cooking a little on warmer days. These considerations are mainly down to where you will be fishing and your personal preferences, but...
Remember that your quarry must not be aware that you are there. A low profile is most desirable. To this end if you are not wading then the posture of your daily supplications can bring an answer to your prayers, but often, even better, being seated is the way to keep low yet still be able to cast and control your line reasonably well. So on your knees, or on your backside, the matter of what you are wearing on your legs and lower loins becomes important.
If you have overtrousers that resist the onslaught of thorns, thistles, puddles and cow pats then your problems are solved more comfortably than with chest high wading stockings. Mine are inexpensive, Goretex bib and brace style trousers with built in braces. Ex-German or Dutch army, they cost about £30 and they are tough enough to last 5 seasons at least. Whatever you do get, make sure you wear them even on hot days. A pair of nice Rohan or Craghoppers outdoor trousers will be cool and comfortable until you start working your way through waist high nettles and thistles, then you will wish you had slipped the overtrousers over them before you decided to angle in places where the fish do not have a well worn path beaten to them.
This is mundane stuff but if you overlook these details it can spoil your chances and your comfort. So please do take it seriously when you begin this toe-to-toe, creeping skulduggery we call dry fly fishing.