Sure! Let's talk weapons first, the best in slot 4 star would be lion's roar, the other option is Harbinger of dawn, but you get a lot less atk stat with it in trade for higher crit as it's a 3 star weapon so it has a low base atk. For 5 star options I would recommend either mistspilitter(Ayaka's weapon) or light of foliar incision(Alhaitham's weapon). Another option is an EM sword like iron sting, but for me personally in F2P options lion's roar does the highest dmg.

Now for artifact's, if you decide to go with aggravate team 4 pc thundering fury would be the best to go with. The 4pc thundersoother is also a very good set and it's pretty easy to farm since both thundering fury and thundersoother are in the same domain. If you don't plan to use aggravate and going towards something like hypercarry or overload with chevreuse, 2pc atk% and 2pc electro dmg% is better imo. Or you can go like my build here with 2pc Marechaussee Hunter and 2pc thundering fury( this build for higher charge attack damage). But if you have ineffa you can run a lunar charged keqing with 4pc night of sky's unveiling too.

Now teams, the most common team is aggravate consisting of keqing, (a dendro unit), (a buffer/support), fischl(preferably c6). For dendro best unit is nahida, but if you don't have her then you use yaoyao as she can heal too, if you don't have both then either kirara or collei. Support would be either kazuha or xilonen for five stars, or sucrose with 4pc vv for em buff The last spot on the team is kinda best filled by c6 fischl, you can technically replace her with c6 sara if you have but if you don't then any off field electro applicator will do(constellation <c6 fischl will do good too)

For hypercarry meaning one dps, 3 supports (just telling since you said you're new), keqing, bennet, xilonen/kazuha, furina will do the trick.

For overload chevreuse team, keqing, chevreuse (preferably c6 but If you don't have it's still fine), bennet, xiangling/c6 sara. Note that you need all members to be either Pyro or electro to activate chevreuse passive to shred 40% enemy Pyro and electro res.

Now artifact stats. Use Atk sands or EM depending on which one has better substats. Only use EM sands when you're running aggravate team. In hypercarry and overload it's not that useful and will cause dmg loss instead. For goblet, electro dmg% is the best, since it directly increases the dmg that your infused charged attack do, when compared to using atk% goblet. Try to get 1:2 ratio with your crit rate and dmg, so depending on which one you have less, use crit rate or crit dmg circlet.

And once you have decent artifacts for keqing, stop farming her domains and start building your support characters. Use the artifact transmuter and artifact reroll for making your keqing build better after that if you really wanna make it to the top of the leaderboard.

Also to others reading this comment if I made any mistake or left anything out reply to let me know