A Question of Price is probably the most important bit from The Last Wish. The Lesser Evil is about Geralt's most well known exploit, so I'd read that. The Edge of the World introduces Dandelion and the Scoia'tel. The Last Wish itself is about Geralt meeting Yennefer.
I assume the one you're skipping is A Grain of Truth. I'd agree, that's probably the low point of the book, and I didn't enjoy it much either, though it does set up Geralt's relationship with most intelligent monsters, and his slight unwillingness to kill them outright. He'd rather undertake his own investigation in such matters to determine whether the monster is really evil or not.
Ciri herself doesn't show up in any of the stories collected in "The Last Wish." I'd look up a fan translation of "Sword of Destiny" for some more quick information on Ciri, and an extension of Yen and Geralt's relationship. The Saga is where the real meat of the Geralt and Ciri stuff comes from.