Hello Showpower
After having ILR for 1 year you can apply for citizenship .If you tell them that you haven't been working during overstay & ask for discretion .If you provide proof who was supporting you during overstay period e.g family or friends with documents like bank statements & if not possible then supporting letters from them stating they have supported you ,this would stop HO thinking you have been working illegally hence you get more chances of discretion being applied in your favour.
Just overstaying isn't enough ground for HO to refuse citizenship & it can be challenged if refused as HO guidance clearly states if overstay is the only adverse factor in someone's good character then it can be disregarded.
Good luck ,I think if you can provide above mentioned you would be successful provided if your caseworker is a nice person. A nice caseworker doesn't mean they don't refuse applications they do but being fair & being fair with you is the grant of citizenship.Another thing it is rare to have nice caseworkers.