If you want to test customer interest in your idea via a landing page, and want to maximize learnings and minimize time spent building the landing page, there are a few options.
1. If you want to rapidly build out a website, the easiest thing is one of the wysiwig platforms. Examples: Squarespace, Wix, Weebly. Squarespace costs money, other two cost less money if you are ok with the URL showing their domain (URL forwarding will take a little more time and/or money). For email capture: All of the above have embedded forms. That said - you can also embed URL from Google Forms or Typeform. The latter is quite full featured and we use it for a lot of programs.
2. If you want to run real experiments (e.g. A/B testing, multivariate) and want to quantify funnel metrics and also run an email campaign out of the same platform, unbounce.com or quickmvp.com are good bets.
For tips on running landing page experiments to test purchase interest, have a look at Elaine Chen's article on Xconomy.