I know it really depends on the quality and popularity of the blog.
Since I am single and mid 30s, my plan is to do a soft FIRE traveling the world. I want to do something while traveling and a way is to write. I know it's a long shot to make several hundred a month as a newbie, but any advice is appreciated :)
It's a bit of a lottery - popular blogs get more readers because they're popular. Starting out, you are (by definition) unpopular, as you have no readers.
Making a few hundred a month as a newbie doing "Yet Another My Travels Blog" is quite challenging. Not impossible, but I sure wouldn't rely on it. You're not offering that much interesting/useful. "Look at me!" is pretty well covered in the modern internet space.
SEO(Search Engine Optimization) is pretty useful to understand.
For something like a travel blog, yeah. You're not really a unique operator in that space. Conversely, if you have unique enough material (being the only source on the internet for things helps), SEO can be entirely ignored, because the content is the SEO. I'm the #1 hit for an awful lot of search queries, and first page for quite a few more.
My blog generates beer money at this point, though the bulk of the value to me is that it feeds me work (battery pack rebuilds/analysis and the like). That dwarfs my direct blog income.
Read up on monetization options. Ads alone don't pay very much until you have massive traffic. There are things like amazon referral links, product deals(this can be tricky though to walk the line between supporting great products and coming off as a shill), patreon, paypal donations and more that may grow your income before your ad income becomes significant.
Even if you have a lot of traffic, a lot of people run ad blockers. Downsides of having a tech audience for me - there's a huge gap between page views and ad impressions. Affiliate links (I generally use eBay because of the nature of my gizmos I work with) are useful, and are about 50% of my direct blog income at this point. I can definitely tell when I've done a post that's affiliate-link heavy (and it's not just spamming links - it's links to the hardware I use in my builds or devices I'm reviewing).
Donations/Patreon/etc are something I haven't messed with, but have certainly considered. Also, turning some of my content into ebooks.
A social media presence is a must for most to keep people engaged.
Also quite true. Which, at least for many of the options, requires posting other material so you're not seen as a spammer. Most of my initial traffic is from those sources, but I don't have much in the way of "direct social media presence" because I value my time...
The toughest is to keep writing even when no one is reading. If you can persist, eventually you will find success of some kind.
True, to an extent. If there's nobody reading, you're just shouting into the void. But posting regularly is important, and my switch to a weekly schedule a year and a half ago certainly forced me to find interesting things to write about.
So, doable, but... another travel blog? Unlikely to be particularly profitable. I'm 2.5 years into my blog project and am still excited when I break $50/mo.