IG prices are often sketchy around key levels, but on the whole OK during trading hours.
They can't allow their price quote to wander too far from actual dma price because arbitrage traders would be all over them like a cheap suit.
You need to also consider bid, ask & mid price, the spread & the fact that you are not dealing with the open market, you are dealing dierct with IG & IG's order book alone (or whichever SP platform you choose) so once you enter a position they CAN & DO skew the price slightly, this may throw you off your game, mostly to force people to use wide stops.
It will take time to learn how the nuts & bolts keep the whole thing together, the process is learned in stages, it takes time to re wire the grey matter, no quick fix etc.
Start with demo, not for too long, then small as possible £pp, build it up & knock it down a few times, then if you have more time to learn & have the stomach for it, it may finally turn around to the stage where you can withdraw money rather than depositing.