I'm new to DIY E-Liquid too. I've made a few batches but have way more to learn.Here are some places I deal with.
Vapers Tek is supposed to have the bomb when it comes to nicotine. I haven't received my order yet so I can't comment personally. It get's high praise in the forums here though
Vapers Tek
I bought my DIY Starter kit from DIY Flavor Shack and I'm happy with it. I also get free no needle syringes from CVS Pharmacy.
http://www.diyflavorshack.com/default.asp
I buy Flavors from
Capellas -
Capella Flavor Drops - Over 75+ Water Soluble Concentrated Flavorings
Hangsen -
BuyHangsen.com
Inawera -
https://inawerashop.com/create_account_success.php
The Perfumers/Flavors Apprentice -
Perfumer's Apprentice
I did buy some Loranns flavors but I haven't decided if I like them yet.
I bought Boston Blue glass bottles from Specialty Bottle Company -
Specialty Bottle - Glass Bottles, Glass & Plastic Jars, Tins, Vials
Don't skimp on flavors or nicotine. Hangsen and Inawera both have high quality flavors. Cappela is good also but I'm learning that you need a higher percentage of theirs.
Put clear fingernail polish over the marks on your syringes so they don't come off.
Good luck with mixing. I find it relaxing, enjoyable, and in the long run cheaper than buying pre-mixed.
I think some of the sites are overseas but you should be able to call your credit card issuer and tell them not to lock your card on purchases from these vendors.