Never had a smart trainer but have used rollers/ bog standard turbo trainer for years until I retired and thank the lord I rarely use either now I can pick and choose the good days to ride the bike. If you're going to train indoors (I'm not knocking it. It was useful when I was working) then you could do with the crappiest bike you can piece together, or that's what I did. It doesn't need brakes or anything fancy. You sweat like a glassblowers armpit, even in a freezing garage, so your frame takes a battering from the salt in the sweat despite cleaning the bike down afterwards. Smart trainers, I'm told, are a game changer but may be out of budget. If you go for rollers/turbo then to relieve the absolute boredom you can find umpteen turbo sessions on YouTube so a laptop would come in handy and a Bluetooth speaker. I've always had to work to a budget and that comes at a cost....boredom. I've never found a static bike stimulating but we're all different. It's better than not training.
