A couple of considerations:
PG could be considered "easier" because it carries flavors a little more readily and is thinner than VG, so it is a little more foolproof with regard to wicking and how it will work across a variety of devices. It also has more throat hit than VG, which some people want while others don't. VG creates more visible clouds than PG and can be considered "smoother" since it has little or no no throat hit. However, VG can be thinned with water, which for many of us makes it work just as well as PG. Most commercial juices have a mix of PG and VG, and ratios vary. Sometimes you will see something like 50/50 or 70/30 PG/VG on the bottle, so maybe you have a preference. If not, don't fret it too much. Personally, I like 90% VG, 10% water and no PG (except some flavors may have it). Some people react badly to PG and avoid it, and a few people can't tolerate VG and don't use it.
For a first effort, if you want to make a VG/PG mix, you might get your nic in one and buy a bottle of the other for the dilution.
Regarding nicotine concentration, the cheapest retail option for long term DIYing is 100 mg/ml by the liter. But that is a heck of a lot of nicotine, so if you are just getting your toes wet to give it a try, that might be way too much. Note that most vendors and vapers will call it just 100 mg, but that is short hand and the real units are mg/ml. You should understand what that means and why it matters if you will DIY, so if not, some reading is in order.
Also, the higher the nicotine concentration, the more hazardous it is. 100 mg/ml (10% nicotine) is the strongest most of us use, because it is widely available. Anything stronger than that and you should be an experienced chemist with a good lab before you open the bottle. There is a lot of info in the stickies regarding that which is worth checking out.
After reading that, if you are concerned or unsure about the risk, you should consider starting with a lower concentration. How low? That depends on what you normally vape. 2-3 times stronger than your normal vape might be a good start. However, if you vape 36 mg/ml, the 100 mg/ml is not as much of a hazard to you, but if it contaminates a food preparation surface or a small kid gets hold of it, that could be really bad. So back to reading the stickies about safety. 60 mg/ml is not a bad compromise for some people, but what is best for you may be a lower concentration, especially if you do not know any chemistry.
On that note, this is chemistry. A lot of people with no chemistry training learn to do this, but they must learn some chemistry to do it correctly. In my opinion, you should understand the following terms and how they apply to this before starting:
- Volume (not the one on the dial of your radio);
- Mass (not the one about going to church);
- Concentration (not how well you pay attention, although that is important too);
- Ratio (OK, I don't have a cute remark about that);
- Safety (yes, back to reading the stickies);
- Dilution (this is what happens when you add orange juice to vodka, for example).
There will be some math involved too. There are good calculator applications that will do the arithmetic for you, but you should know enough math to understand how the numbers affect what you will end up with. I recommend downloading at least one calculator and trying to make some imaginary mixes with it to ensure you understand how to do it.
Finally, if that all sounds like way too complicated of an answer to a simple question, you might reconsider whether DIYing e-juice is for you. If you start reading the stickies and decide it is boring and not worth your time, DIYing is definitely not for you.
