>>9022084Vehicles are definitely a good investment. I personally advise all army men enthusiasts to have at the very least a set of tanks. You can branch off into jeeps, trucks, helicopters, and other such things from there.
As for your picture, I would guess that they are all from a dollar store, but the figures themselves are good-looking to me. A big part of that is in how the figures are posed. While Tim Mee is the go-to brand for high-quality army men, the uniqueness of their poses are rather limited. Here's a picture of some of my BMC soldiers (four on the left) and vintage Louis Marx Company (eight on the right) men. In addition to straight-up combat poses, they can march, melee fight, charge, and carry wounded soldiers (the one on the end). When was the last time you saw a plastic army man just walking around with their rifle slung on their shoulder? So when you're getting army men, I recommend getting Tim Mee soldiers for a default set of battle poses, and then go to other sets (including dollar store ones, if the quality looks good enough) for more experimental poses.
>>9022089Engaging with plastic army men as a hobby is really a giant spectrum. What you want to do with it really depends on what you are personally into. For me personally, I like to play with them just as straight-up toys in my own fictional universe, pose them for photography (like the pictures you saw earlier), and collect them as an extension of my figure collecting hobby. The time period of the soldiers are really varied, too. The standard Tim Mee army men are tangentially based on Vietnam War-era U.S. military aesthetics, while other brands like BMC are predominantly focused on World War II, and more collector-oriented brands like Armies In Plastic do more Napoleonic-style historical sets. Whatever you decide to do, the hobby is really fun, and I can recommend some figure sets and vehicles for you to get started as well.