A. I do not know where you stay and where you intend to start your business. The first part of what you have in mind is the 'PERSONALISED GIFT THEME INDUSTRY'. This is well established. Regarding your T-shirt, mug, plate and case cover printing, there are many firms already doing it on a large scale via the online mode offering door delivery and in-store collection (printo.in,vistaprint.in,inkmonk.com, printland.in,printvenue.com).
Apart from this, the local photograph studios, wedding photographers also offer this service right from the branded ones like GK Vale to the small shops all offer mugs, plates, T-shirts etc. Even Archies offers these services online and in shop too.
So, do your local research and then think of venturing into this, do you have a potential market? If you do, then do not limit this only for the shop related foot-fall of customers, approach retail brand chains, offices, MNCs, colleges etc where in they have a large team and need team promotions. This will bring you a regular flow of orders.
B.Shoe manufacturing is again a large industry, you just need to visit the local markets where in we get reasonably good shoes for Rs.399-499 (Metro India, VK exports in Karnataka). Again the online market is statured and all popular platforms offer this ( amazon,flipkart,snapdeal etc). So, again do your research.
Both A and B are different streams of businesses, think, lay out your ideas, sit with someone you know who is already doing this. This considers the initial investment and the overheads which will include the supply chain from the raw materials to the final delivery. I feel it would be better to stick to one, A or B, do a local on-ground check in your area about the estimated supply and demand for the products and how you can make a difference. Then you can follow the suggestions given by the above experts.