Step 1 - type several seed keywords into Ahrefs and hit "search" to find a few million keywords you can filter through
Step 2 - use the filters to find long tail keywords that meet ALL these criteria....
2a - have a keyword difficulty score (KD) of 3 or less
2b - have a number of words of 6 to 10
2c - there are at least 1-2 websites ranking in top 10 of google that have a DR of 20 or less
2d - there are at least 3-4 websites ranking in top 10 of google that have 0 backlinks
2e - there are at least 2-3 websites ranking in top 10 of google that DON'T have your keyword in the title of their pages, and they also don't have your keyword's search intent in the title.
For example, these 2 keywords look very similar because they have almost the same words, so you might think that they are similar and can be included in the same article. Well, it can be included in the same article because they share the same topical relevance, but their search intent is completely different:
how to move a car with a dead battery
how to start a car with a dead battery
As you can see, the first keyword refers exclusively to MOVING a car whose battery is dead, while the 2nd keyword refers exclusively to STARTING a car whose battery is dead. So, at a first glance, both these keywords could be included in the same article without an issue (they can!) and they will both bring you traffic. However, for a newbie to SEO (and for a new site in general) it's easier to rank in google if you target these 2 keywords separately instead of putting them in one article because you can on-page optimize them better and since they are both low competition you will also have to create less content for each article, and also need less backlinks (if any at all) for each of these articles, too
Step 3 - use a tool like Frase.io (you can get it for $5-6 a month with group buy tools), or you can manually go through the websites in top 10 to see what kind of content they have. You will want to check, and take note of all these things...
3a - the search intent... the first, and most important thing you will want to check is how many of those websites address the exact search intent of the keyword. Many times you will see that websites put the keyword in title but they target a different intent with the article. That's good news for you because if you match the search intent better than your competition the traffic will flock to your article instead of theirs, no matter how high your competition DR / DA / RDs and backlinks metrics are. I've seen this happening numerous times for low competition keywords when I did keyword research in Ahrefs earlier this week, so this shit is real. If you match the intent of the keyword the traffic will prefer your content over your competition's, which in turn will increase the popularity, authority and - more importantly - the rankings of your website;
3b - the number and name of the sub-headings.... again, use Frase.io or manually open up all of the websites ranking on google's 1st page in new tabs and have a look at how many sub-headings those 10 websites have, and what they talk about. If you see that the lowest number of sub-headings is 4, for example, you will want to include at least 4 sub-headings (H2 and/or H3, depending on which ones make more sense) into your content. Sometimes, you might get away with fewer sub-headings (especially if the competition is really really REALLY low, like for example, none of the websites in top 10 of google targeting your keyword, or their content is low and garbage, or the DR of most of those websites is less than 10, or 7-8 of your competitors have 0 backlinks, etc), but in general, it's best to include at least as many sub-headings as your competition has. So, for example, if the lowest number of sub-headings is 3, and the highest is 6, you can have 3-4 sub-headings and if all other important elements that I'm describing in this comment match your competitors' you're good.
Also, take a look at what those sub-headings say, and match that! You don't want to copy/paste the sub-headings of your competitors in your article. just look at which topic / keyword they are addressing with those sub-headings and then rewrite those sub-headings in your own words and include in your content only the sub-headings that make the most sense to you, and which are obviously relevant to the intent of the keyword you are targeting
3c - content length... if the websites ranking in top 10 of google have an average of 800 words (just an example) you might want to create 800ish long articles, not 4k-5k words long article. Personally, I only check the sites ranking in top 5 and do the average of those, because if I can mimic what the top 5 ranking websites do I will have no problem ranking in top 10 anyway
3d - images and image ALT tag.... again, have a look at the number of images that the websites ranking in top 10 have, and make an average of that number and use that many images. This sub-step is actually not that important, and if your content matches the search intent well and all other on-page elements are good you might rank with a single image, no problem. But, for extra peace of mind I sometimes do check the number of images my top 5 competitors have and if I feel like it's important from a user experience to have at least that many images I might add them. Otherwise, just add your target keyword in the ALT tag of the 1st image on the page and you're good
3e - other on-page optimization.... make sure the first 3-4 sentences (first paragraph usually) of your content is manually written and 100% unique, and then add your keyword in the first 1-2 sentences of your content, and call it an article.
Step 4 - optional, and unnecessary most of the time if you've done your keyword research properly, but.... backlinks. If you've done all of the steps above and you're still not ranking in top 10 without a single backlink in 1-2 months, it can only mean 1 of 2 things: your website stays in the sandbox longer than normally, in which case I don't know what to tell you because google is more moody than a frustrated wife, or you need a few dofoll0w backlinks. Normally, if 5-6 or more of your competitors have 0 backlinks (as shown by Ahrefs) it means that they either have their backlinks hidden from crawlers, or most likely (as it usually happens with low tail, low competition keywords) their domain has bigger authority than yours (which is normal since your domain is new) and all things being equal google does favor higher authority and aged domains over new ones, so in this case you might want to get a few dof0llow backlinks. Just check what type of backlinks your competitors have and try to match those or, if that's not possible just get a few backlinks from web 2.0s (you can get these for free) and point them to the article you are trying to rank, but make sure you diversify the anchor ratio to avoid getting penalized. Let's say that you are getting backlinks from 12 web 2.0s (again, just an example, it could be 3 backlinks, or 17, or whatever other number you choose).... Well, of those 12 backlinks you will want 1 or 2 of them to have the exact same keyword you are trying to rank for as anchor text, but all other backlinks should be completely different (branded keywords if your website has a brandable / catchy domain name, naked URLs, generic terms like "visit us" / "click here" etc)