I just got back into vaping after a long break. Honestly, I think that the Eleaf iStick Pico is one of the best "starter" devices on the market. I have purchased three of them since March.
They do the basics really well while having some more advanced features like Temperature Control built in as well. At the same time, the advanced features don't get in the way or clutter the device and interfere with it being used simply and intuitively to start. It's definitely something that a beginning vaper can grow into with time and not have to go out and buy another fancier device. Another plus is that it's relatively small and light so that it can go with you just about anywhere and everywhere. It uses a removeable 18650 battery that can be charged inside the device with a USB cord, or can be removed to charge with a stand-alone charger. As battery technology advances, you can get newer/better/longer lasting batteries for it without replacing the entire device. Even the firmware is upgradeable on the Pico. I haven't played with it yet, but I will likely start playing with the Arctic Fox firmware on one of my Pico at some point just because I'm curious.
I did just get an AL85 or "Baby Alien" and I like it. Basically a slightly bigger Pico that can use tanks that are 25mm in diameter instead of the 22mm that the Pico is limited to. It seems like it has a few more features, but the screen is more cluttered and seems a bit more complicated than the Pico. I'm sure it seems that way because I'm not used to it yet. The biggest negative to it IMHO is that the firmware isn't upgradeable like the Pico, but that's probably not a huge issue for 99% of normal users.
Pair the Pico with a Kangertech Subtank Mini (aka "STM", which is what I have used for a few years, or alternatively a Toptank Mini, which looks to be identical except it can be filled from the top without removing the tank), and it would be hard to beat for both ease of use for a beginner AND upgradeability and room for growth and experimentation. There is a wide variety of premade coils available for the Subtank Mini, which they call their "Organic Cotton Coils" or OCC (or SSOCC, the SS meaning Stainless Steel for the material used in the housing - not to be confused with the stainless steel wire coil that can be found in some, but not all, of the SSOCCs) for different vaping styles. The OCCs and SSOCCs are plug-and-play. The STM also comes with a rebuildable deck to use if/when you want to start wrapping your own. Even some of the premade coils can be rebuilt with a little effort and a few minutes watching Youtube how-to's. There also seems to be a wide variety of different aftermarket parts available for the STM to play around with different sizes, styles, and materials used for the tank.