Welcome! You've come to the right place.
First of all, you MUST stop straightening your hair. I, too, was a flatiron addict for years. It's hard, but your hair will thank you!
Second, your dandruff problem may stem from the yucky chemical buildup FROM your shampoo/conditioner. The key to knowing what regimen is right for you is by simply experimenting and getting to know your hair in its natural state. I can use Wen (a cleansing conditioner--expensive but my whole family of curlies refuses to use anythng but!) as little as once a week, depending on how dirty/sweaty my hair gets. If you have an oiler scalp, you may have to go the lo-poo route.
Steer clear of silicones and sulfates. Most popular brands contain these, with the exception of a few.They initially make your hair look shiny and healthy, but they end up doing long term damage. You can find plenty of recommendations on this site for good silicone/sulfate free shampoos. You may even find that you don't even need shampoo once you have rid your scalp of all the nasty chemicals!
Hair loss is categorized in a few ways. I had three periods where I lost large amounts of hair (due to illness). This type of hair loss (biological) has nothing to do with the condition of the physical hair. The second type is due to excessive chemical treatments/hair coloring/heat damage/other physical stressors (for example, ponytails or buns that are too tight). I am guessing you are the second one.
Poor nutrition can affect the state of your hair. If you are not getting all of your essential nutrients, your new, virgin hair may grow in dull and weak. I have a problem getting all of my vitamins, so I take a daily multivitamin in addition to Healthy Hair, Skin, and Nails by Andrew Lessman. Hair growth typically takes a while to start, but you'll soon begin to notice faster, healthier hair growth. It also causes my nails to grow crazy fast, which is an added plus
You can find these supplements at Target, Walmart, or Walgreens.
Otherwise, there aren't a whole lot of routes to make your hair grow faster. You may consider starting "fresh" with a new haircut to chop off any yucky ends. You will be shocked at how much thicker, healthier, and maybe even longer your hair looks! Try to find a hairdresser with curly hair experience. There's a "Salon Finder" tool on this site that will help you find someone in your area. Spur-of-the-moment trips to any open hairdresser usually doesn't end well for curlies.
Finally, experiment with products and oils to maximize your curls without stripping your hair. I use a combination of products, from a standard jar of extra virgin coconut oil to curl-specific mousse. I would recommend steering clear of any popular, commercial, "general-use" hairspray. These typically contain bad alcohols (there's a list on this site somewhere that lists "good" and "bad" alcohols) and all sorts of other nasty chemicals.
Have you discovered your hair type? Exact typing is not essential to taking care of your curls (hair is hair, after all!), but knowing whether you're a 2b or a 4b can help you figure out a good product regime. Look for profiles of people with similar hair as you have, and then see if their regime can work for you.
***Keep in mind that your hair may change as it gets healthier and if you cut it. Mine was more of a 2c when I was frying it, and now it's slowly creeping towards 3b as it goes longer without excessive heat or chemical damage. Do not get stuck on a particular type, but knowing the properties of your hair can help!***