I'd use glass bottles if you're using any kind of heat for your steeping.
Other than that, I always use only these 3 types of plastic bottles for mixing and storage of my eliquids: PP, LDPE, and HDPE. They cost alittle more, but are higher quality plastics with more rigid manufacturing standards than many on eBay or Amazon, which are usually from China and are not one of those 3 types. You definitely don't want #1 PET bottles (like sodas, bottled water, etc. come in) which are for 1-time use only, nor the #7 OTHER bottles which can be a mix of resin and other materials! The #7 plastics have been found to release BPA, and have been banned for use in baby bottles and sippy cups for kids, and in many other products.
Here's a bit of information on leaching and plastic bottles:
"To be certain that you are choosing a bottle that does not leach, check the recycling symbol on your bottle. If it is a #2 HDPE (high density polyethylene), or a #4 LDPE (low density polyethylene), or a #5 PP (polypropylene), your bottle is fine."