I just started, but took the 'mix by weight' route. I bought a 30$ scale, a quart each of PG and VG, 120 ml of 100mg nic, and 7 or 8 flavorings. I saved and reuse a bunch of bottles from premade juice. Masking tape for labels (for now). I transferred PG and VG into 8 ounce squeeze bottles that I picked up for 95 cents each at a local kitchen store. I find it to be accurate, fast, and simple with no cleanup required. As we don't know OP's budget restrictions, I can't say if this is inexpensive enough or not, but the cost savings is tremendous, I plan to continue, so I wasn't concerned about saving a few bucks here and there.
The real cost, of course, is falling head first into the DIY rabbit hole