1. Figure out what value you will provide that isn't already being provided by someone else, or that you can provide better, and that a lot of people will care about. Leave your ego out of this.
2. Have a concrete plan to keep your site updated frequently. Lots of people start their sites out strong with two or three good ideas for content. Once they've worked through those they lose steam and the site flounders.
3. Figure out how you will get traffic. Putting a site out there and waiting for people to discover it is seldom quick. Expect to work on publicity.
4. Figure out how you will earn income from your site. Most travel sites and nearly all blogs are free. There are options, but they involve work too. (That word "work" keeps coming up. Sorry about that.)
5. Don't expect to get rich. Income from these sites is nearly always negligible. We read about the exceptions and don't realize how unusual they are. The most you can probably expect is a bit of income to offset some of your travel expenses and (in the U.S.) a tax deduction for the rest. (You can't take this deduction forever, or the IRS will decide that your "business" is really a hobby.)