For my kid, we want to buy a first piano keyboard.
There are nice options under 200 EUR.
But now we have a dilemma:
In range around Yamaha PSR-E363, Casio CTK-3500,
or with lights: Yamaha EZ-220 (or some better), Casio L or LK series.
Without. Point blank.
Lights look fun to start with, but a beginner will end up watching them rather than learning to read.
Note, you can usually switch them off, so you don't have to choose a keyboard that doesn't have them.
I have no recommendations on mobile teaching apps, I've never used them.
Don't bother with lights. The player will be forever chasing them. In fact, for a few weeks I recommend not trying to read dots either. Just get used to the instrument, what it can do, and have fun.
I would hope that pound for pound, a keyboard without lights would have other, better features.Most will have speakers or a headphone port. Buying pre-loved will generally get you a far better instrument (my opinion!). And DON'T write letter names on the keys - or even use stickers!
Its only my opinion, but my observations in the music store are such that they lead me to think the lights on these keyboards serve one purpose, to sell keyboards. I've never known any teachers that use them to teach with, and I've never met anyone that actually learned to play music that way, so in my opinion the lights are a sales gimmick but an effective one. Whether you wish to learn to play by ear, or you are interested in learning to sight read and play that way, I can't think of a way that the lights will help a person become a musician either as a solo player or a band member. But maybe some one knows an application I haven't thought of myself.
Your question contains a crucial misunderstanding in the two words
piano keyboard
The defining feature of a piano keyboard is weighted keys, emulating the hammer mechanism of a real piano. Most teachers recommend learning with weighted keys, because otherwise kids get used to keys which take little-to-no force to press, and this makes it significantly harder for them to move to playing an actual piano.
As far as I can see, none of those keyboards have weighted keys. Keyboards with weighted keys are a bit more expensive.
So you need to think more carefully about how far you think your kids will go with playing the keyboard. If it's just going to be a toy they mess around with, then of course go as cheap as possible. But if they're going to be playing it more seriously and getting lessons, then get something which is a proper musical instrument to support their learning.
All the various gimmicks to plug in or light stuff up are just that - gimmicks. Don't bother.
Lighed keys are unnecessary and counterproductive. For some serious piano learning an 88 key with hammer action is essential. Entry level digital pianos made by Yamaha, Kawai, Casio, Roland, Korg are available, but you have to double the budget. A Casio CDP-S100 is the cheapest option at the 360 Euro price and could run on alkaline batteries. Roland FP10, Yamaha P45 and Korg B1 are all around of the 400 euro level.
But for a first run a smaller 61 key keyboard with VELOCITY SENSITIVE KEYS is the minimum baseline. Even with a spring action the speed of the key press will affect the sound volume. Going for a Casio CTK 3500, or a CT-X700 a Yamaha CPT360 or PSR-E360 could be an idea. They have rhythms and nice sounds that could make more interesting the thing.
Another aspect of the lighted keyboard is that doesn't help to get the ear, because instead of associate a sound to a key it associates a light to a key, and anyway music teachers tells that looking at the keyboard it's not a good idea, one has to train the finger to find the correct distance. Actually one of my piano teacher made me practice with a cardboard kiding the keys sometimes. So is important to have standard sized keys.
Sight-reading is paramount to learn to play music especially classical, as with solfege, but lighted keys here are steering in another direction.
In my opinion, you should not consider buying a keyboard with key lights.
The lights do not help in any way to learn how to play keyboard. I would even say they distract from learning because your child will only watch the light patterns and try to "catch" the right keys in the right moment. It will not understand the connection between keys and corresponding tones, nor which fingers should be used to play melodies without cramping the hand.
