New to extensions......PLEASE HELP

Hello all.  I am a hairdresser looking to add hair extensions to the services I offer.  I have been scouring the internet and OH MY GOSH !!!  There are as many selections in this world as there is wine.   I am looking for your professional opinions and tips as to which brands you feel are the best, most economical, etc.   So let me get this straight... there are MANY companies that offer their 'own brand' of extensions (adhesives, applications, training etc. )  as well other companies that sell just the remy hair and others you can buy just your preferred type of bond and educate yourself.  I hope I am making sense with my questions.  Any help would be greatly appreciated, as I am feeling overwhelmed with all the choices.!!

I am located in Washington State.  What are your personal preferences?  I am thinking about starting with the hot fusion method.  If there are any most important tips you can give, that would be wonderful,  thanks!!