Covers33 indeed do the best deal for both inners and outers.
I buy poly lined inners - because they offer completely clean and smooth antistatic environment for direct contact with the record.
For sleeve protection I buy their 400 gram poly sleeves instead of the more common PVC sleeves. PVC sleeves ripple over time if records are stored to tightly and the heavy duty poly sleeves remain smooth and slide easily without sticking.
One other thing I do is keep the original inner with the record - the original sleeve is part of the record's 'history' and in some cases they add to the value of a record if it's a bespoke design, coloured, or lyric inner.
Good luck with the cleaning - I try not to do more than a hand full at a time with my Okki Nokki - I lose the will to live after cleaning more than 10 or so.