Is it good?: The champion you're using to climb doesn't really mather as long as you're doing it properly, since the amount of errors people commit in Solo Queue is high enough to dismiss a Champion's Kit lack of strength. In lower rankings what matters most is Shared Skill (those things which no matter what the circumstances of the game are, you should be able to do properly, such as Farming, Wave Control, Decision Making, Movimentation, etc)

Nonetheless, incase you wanna commit to playing Katarina in rankeds, TIPS AND TRICKS!: -Yellow Trinket + Shunpo to evade from a gank or chasing -Katarina is often bullied in lane, if you're getting zoned away from creeps you should be using your Q to last hit only, as it is your only ranged skill -Q > E > W > R is the common assassination combo -Max Order is R > Q > W > E

Matchups: Katarina is bad in general in the lane phase, so most matchups it is common to fall behind in CS, but Katarina's strong point is teamfighting and objetive contesting

Masteries: 12/18/0 for Masteries, going for Sorcery, Double Edge Sword, Natural Talent and Bounty Hunter in the Ferocity Tree, as for Cunning, Savagery, Secret Stash, Merciless, Dangerous Game, Precision and Thunderlord's

Builds: Start off Boots + Pots if you're laning against somebody who throws lots of skillshots in order to dodge them, otherwise go for Doran's Shield + Pots. The first item depends on your lane matchup, it could be Abyssal Scepter or Zonhyas, depending on AD/AP matchup, but incase you're feeling comfortable, you could go for a damage oriented Luden's Echo. Katarina's endgame build is composed of: Sorceress Boots Green Enchantment, Zonhyas, Void Staff, Rabadon, Rylai's, Banshee's, other situational items are Luden's and Abyssal incase you built it earlier.

Spells: Flash + Exhaust against Assassins or Ignite against every other case