if i opt for a 2400 g will it bottle neck my gpu ?
For processor or for GPU? which games? what resolution? one of the two will absolutely bottleneck, always...and so will a 2080ti/9900K combo. Go check some 2400g reviews to find out how it works:
https://duckduckgo.com/?q=2400g+reviews&t=ffnt&ia=web
https://www.newegg.com/Product/Product.aspx?Item=N82E16820164118R
That's a stick at $49.99, open box. There are other brands at even cheaper but IMO brands that are sketch.
But here's the thing, if you ever want to go two sticks to get 16GB in dual channel it will not likely work, even if you find same brand/model, at high clock speeds since they won't be a matched pair . It might, but you can't count on it.
ADDED: If you want a bit of advice for how to compromise and leave yourself in position for upgrading...get a 2200g processor for now, with money saved get 2x8gig ram. Then when you get the money move up to a decent GPU and overclock the 2200g even higher...it's gonna be a decent gaming system, even with 4 cores, as long as you're not streaming or other multi-tasking.
If you're on a decent mobo (like the B450 Tomahawk) you'll even be able to drop a Ryzen 3rd gen processor into it in a year or two for another decent upgrade and then start streaming.