We recently bought a game called the sneaky snacky squirrel for a 4 year old and it was a hit with child and parent. I also always add a book when I buy a gift for a kid.
Here is a C/P of my 4yo DD's Christmas List if that helps prompt ideas
American Girl Doll books - She has the first book for Kit, Julie and Rebecca (Rebekah?) and loves those three characters, so more books in the series would be good.
She is also in to her stamps a lot lately (like the ink pad kind of stamps) she has some farm and sea animals, but would always love more.
Puzzles are still a huge favorite. No smaller than 100 pieces (fewer pieces are too easy now), and the 'lenticular' puzzles (like the multi-dimensional, looks different from different angles) are too hard.
The character-type toys that she likes are Littlest Petshop, strawberry shortcake, Olivia the Pig, and of course the Disney Princesses
She is just starting to like 'big kid' Legos and will get a small set of those from us for Christmas
Santa is bringing her some PlayMobil starter sets
Also, if anyone knows where the old wooden block set is that all the grand-kids played with, she would LOVE to have a turn at those
She could really use some sort of jewelry organizer. She has a caboodle, but it isn't really working for her. Maybe a necklace tree or something like that.
She has also been asking to go see a play - so maybe certificates for the Children's Theatre or Stages Theatre (I think that Stages is WAY more reasonably priced than Children's - at least the times I have looked)
The bathroom downstairs is going to be Livie's bathroom, so maybe a fun shower poof and cute kid bath/shower set would be fun (Dr. Baron said no bubble bath)
Target has a $20 pedicure set in their arts and crafts aisle that DD got as a gift last year. She LOVES that thing. I give it at b-day parties a lot and it is always a hit. If your budget is $50, you could add some fun nail polish or a purse and other accessories or something.
From another perspective ... For the love of god please do not buy my kid leap frog anything. She does not need, and I do not want her to have, another electronic toy. I have a bin of leap frog stuff that never gets played with. My in-laws see leap frog and think "oh, this must be educational" when really it is a screen with some crappy buttons. Ewww. My DD would rather do math worksheets (seriously) than play with leap frog stuff. Maybe we are just weird, but I can't figure out what parents/kids like about leapfrog.
DD is 4 and she likes anything that promotes pretend play. 1. My Little Ponies or any kind of Little Pet Shop people 2. Barbie (this is new) 3. Doctor Mommy Doll is a HUGE want on her list and really Doctor anything. She examines her dolls, her stuffed animals, her father and I... 4. The Lego Duplo sets...especially if it's pink or purple 5. Build-A-Bear anything 6. Play food, coffee makers...or anything that can be used to set up a pretend meal/tea etc. She has a Melissa&Doug cake that you can cut into slices and has taken to having birthday parties for her various toys
craft stuff: watercolors with real watercolor paper, googly eyes, pipe cleaners, colored tape, glitter glue, put it all in a container and you've provided hours of consumable fun.
puzzles are huge right now. there is a melissa and doug block piece puzzle that's good. or crafts from Michael's - the foam sticker craft sets are easy and fun.