Stovetop does not make espresso. Its makes strong coffee.
Its absolutely fine for a decent cup of coffee. You want a grind which is between espresso, which is like sand, and cafetiere which is what you get in ready ground bags.
Unless you have your own grinder, its worth going to somewhere like http://www.thebeanshop.com and get some ground for you.
A 3 cup pot will make 1 mug of coffee. If you water it down, it’ll make 3 cups of americano. But I prefer to drink it straight, as it’s pretty weak otherwise.
If you go down the espresso machine route, you can make a shot of espresso and water that down to make americano. It will only make a single cup again though, as any more than 15 seconds with an espresso machine will start to taste bad.
If you do buy an espresso machine, you really need to buy espresso ground, in the supermarket you’re Limited to one or two packets that will be ground to espresso size, otherwise you’ll end up with ditch water. So again, best off buying direct from a bean shop.
Personally, I’d start with stove top. And then go onto an espresso machine later. A Bialetti is cheap, an espresso machine needs to be an investment. Once you learn to love coffee, then is the right time to spend the money, and then buy a burr grinder to grind your own. You’re looking at £300 though really to get there. £15 will get you a bialetti, £5 will get you a packet of ready ground for bialetti.
Cafetiers can make decent coffee too, and the bags in supermarkets are ground for them, so lots of selection. Nothing beats just roasted, just ground, just brewed in a decent machine, with a decent portafilter basket.