Armouries museum within walking distance of centre is definitely worth a visit especially if demonstrations in the tilt yard outside are going on.
The arcades referred to are the ‘Victoria Quarter’ which features swanky shops including a branch of Harvey Nicks which (largely) run off Briggate.
For a snack/coffee/tea break visit the Tiled Hall Cafe in the Art Gallery/Library building next to the Town Hall (which you can’t miss!). There used be tours of the Town Hall but there is some renovation going on there currently so I’m not sure if they are still on. There are free chamber music concerts at College of Music 1.00 - 2.00 pm - not every day though - you can pick up leaflets for these.
Kirkstall Abbey (ruins of Cistercian monastery built 1215) are situated implausibly just out of the City Centre by the River Aire and are about as far as you could sensibly travel by bus and back in half a day. The Abbey House Museum across the road is also worth a visit and also has a cafe attached which you can visit separately from the museum.
I’m a born and bred ‘Loiner’ (native of Leeds) so if there’s anything else you see that might float your boat, then feel free to ask! I have said in these very pages before that while Leeds is hardly ‘tourist central’ it does have its charms!