Have a look at the Hawke vantage range if you want something that is budget friendly. They have a good reputation with the air rifle community for been good enough to use for target shooting.
To be fair, it'd be perfect for an AEG due to "1"x magnification (bracketed because it'll never be a true 1x, it's impossible), but as a sniper optic a 24mm diameter lens doesn't get enough light and it's gonna kill the already limited fov you get with a magnified optic..
Ask a friend to try a proper 4x32 and then a 4x24, you'll see the difference..
2x is more suited to airsoft than 3x. And easier on the eye when picking up targets. It's got a couple of meters more FOV at the lower end as well over the 3-9x even with the smaller objective lens.
Just make sure you have a 25mm mount system, If you don't then you can pick them up dirt cheap (uttings are expensive for mounts). Ebay is best for cheap ones.
the 2-7x32 can be had for about £60. Doesn't have the illuminated reticle but it does have a half mildot version.
https://www.uttings.co.uk/p121296-hawke-vantage-2-7x32-ao-rifle-scope/#.W9rT7jGYRog
If you want the illuminated reticle they retail at about £90 for the same sight.
https://www.uttings.co.uk/p120559-hawke-vantage-ir-2-7x32-ao-rifle-scope/#.W9rTsTGYRog
Only issue you might have with them is the length and weight.. But the performance should be well over what you expect.