Since your still learning how to play, don't play random leaders yet. Pick Darius to learn the ropes of a strong economy as this is your primary problem. Financial gets you more commerce, prioritize Pottery and building cottages early on. Also try and look for a strong riverside start. Organised reduces civic upkeep costs directly giving you a moderate GPT saving which can equal 10-20% on the science slider, plus you get half cost courthouses. After researching pottery, bronze working, and only if you need it animal husbandry, then research Writing > Alphabet > Currency > Code of Laws (don't worry about getting to CoL first, don't waste time with the priesthood line as you will want currency). Use alphabet and not maths at first because you won't be a pro at tech trading to obtain Alphabet from the AI yet.
When you get Writing which should always be an early priority, start building a library in all your cities, and use Slavery to whip them asap, then follow up with Granaries (by then you should have 3-5 cities and no more than this with at least 1 worker per city). As soon as the libraries are built, fill as many scientist slots as you can once each city reaches its happy cap, and build up to 7 maximum cities before you reach CoL. Once you have Alphabet start producing research to get Currency faster, and once you hqve Currency, start producing Wealth to get out of low GPT and increase the science slider (only do this in any city that has already finished a library and granary). Once you have CoL, build a Courthouse in every city using slavery again to get them built ASAP, and only then begin expanding to 10-12 cities. Once your core cities have a Library, granary, courthouse and aqueduct built, swap them over to producing wealth or research while they grow. You might also want to build forges prior to this as well, but that's not as important as getting those 4 core buildings built. Oh, and for
just use hereditary rule at this point, don't worry about
A good strong tactic to learn how to do for every game you will ever play is getting to 7 cities and CoL in as little time as possible. But you have to make sure not to simply spam 7 cities asap as you will need libraries before going over 4 or 5 cities to keep your tech rate high enough with scientists.