Hello Shuck,
it is good practice to tie more than one of any fly but to tie dozens when you first start out is a bit extreme and you will also find it boring. You are best starting off by tying 6 of a pattern in 3 different sizes starting from the larger size and working down to the smallest size. Each time you finish a size, compare the first fly with the last and once you have done all 18 then compare the first largest with the last smallest. Doing this enables you to see your progress as you tie and helps you consolidate your skill with one fly.
Here is a link to a step by step I illustrated using that very same method - Step by Step - we do a lot of this type of tying across the pond and the SBSs are to help anyone of any level in tying flies.
Start with simple patterns that do not require you to go out and buy masses of materials, master these before progressing to different fly types and tying methods and you will get a lot of enjoyment as you progress and hone your fly tying skills.
Some simple fly suggestions - Griffiths Gnat (without the peacock herl), a generic black fly, a simple thread and hackle spider (these are quite easy to master and you can create several different spiders just by varying the thread colouration)
Search the web by all means and you will find a wealth of patterns from the basic beginner flies right up to the advanced level Salmon flies that take years to master correctly but above all, have fun doing so!
TLs