Welcome GM. I'd suggest reading a lot on
http://www.m4carbine.net/forum.php about best procedures and who has good vs awful youtube how-tos. And research what specialty tools make the assembly easier. Here are some I consider indespensible:
Long bolt-catch pin starter punch
Magwell and upper receiver vise blocks
Geissele reaction rod
Magpul armorers wrench
Plus sets of roll pin and flat tip punches
Smaller (~1") ball peen hammer and rubber/plastic mallet
Lubes and grease. I like Slip2000 CLP, Weaponshield general grease and Aeroshell 33MS barrel nut grease.
Good torque wrench
I would definitely begin with building a lower receiver. A billet can be simpler to build with a screw-in bolt catch pin and integrated trigger guard. I prefer forged (Mega Gator) as they are light and cheaper. Just be careful not to break the ears pounding in trigger guard roll pin. A stock AR mil-spec trigger has a fairly heavy pull weight and are often gritty so I would buy a parts kit without trigger or pistol grip and add what you like. An ALG ACT trigger is smooth with mil-spec pull. A Geissele is fabulous with various single or two stage weights, but expensive - ~$200 on sale. I love the SD-C.
For uppers first decide if you want a rail with folding sights or A2 fixed front sight/gas block. I like both, but the fixed limits you to shorter rails and the gas block pins can be a bear to remove.The newer rails with low profile barrel nuts eliminate the need to time for the gas tube. Be aware of the inside diameter of rail to insure clearance of gas block.
I would get a barrel with a lo-profile gas block already installed. Lots of good options out there. Here is one:
http://ballisticadvantage.com/16-inch-2 ... arrel.html Theses dust covers are great. Easy on/off and no long pin that requires removing the rail to take off.
http://www.primaryarms.com/strike-indus ... -223-01-bk