Shopping is not an activity where the bored mistress of a household or the foppish lord go seek out ready made gowns and boots, picking armor off the rack or ordering a take-home meal, servants trooping behind them to carry boxes and bags of goods. Shopping is a fairly complicated system, but it isn’t impenetrable, and it’s ample opportunity for roleplay.
It is infrequent that a knight or man-at-arms of any stripe would find ready made weapons and armor. Many pieces of fighting equipment are made to the size and weight of the wielder, as well as any additional specifications they have - Tyrion’s eating dagger would be of a different heft and style than Ser Duncan the Tall’s. A nobleman looking for an eating dagger may be able to find one already crafted, but like as not he would want one with his House’s sigil; a knight in search of plate armor would need his measurements taken, a man-at arms in want of a sword would need to make sure the hilt was just so.
With these complications, an acquisition might take more than one visit to the blacksmiths and armorers: once to have measurements taken and discuss the project, a second to check up on how things were progressing (for a sword might be a week in the making, armor a pair of weeks or a month, or even longer depending on its complexity), and a third to pick up the goods. One might choose to have a piece of work made by a journeyman rather than by a master craftsman to save on costs - or one might insist on masterwork.
Clothing, like armor, is not a ready made proposition. Anyone in a position to buy new clothing would also have a multi-phase process, either going out to a seamstress or tailor, or - more likely if the character is of a high rank - having the craftspeople come to them. A tailor might come bearing samples of bolts of cloth, a knotted cord to serve as a measuring tool, and a handful of scampering apprentices, the better to do the necessary work swiftly.
Again depending on the complexity, and if the material available suits the wishes of the noble, the project would begin: a simple chemise or kirtle with no embroidery could take a few days (shorter if multiple people pieced and sewed it), and more complex gowns could take weeks or even months to come to fruition. Everything would be done by hand, and the more complex the matter - adding in beads or chips of gems - would require additional craftspeople (a gemcutter to handle the gems and drill them, for example). If there was no material available that pleased the noble, it is possible something could be purchased, or even woven on request: such weaving of material (particularly damasks or similar) could take many weeks in and of themselves.
Bearing this in mind, many nobles would lay out significant amounts of money to ensure their clothing was of highest quality, and care for it well, to be certain that the garment would last for years. It would often be mended, and when it was in disrepair, it may even be eviscerated for salvageable parts - fur trim, the gems and gold or silver threads, etc. Pieces might be patched together into new garments, or used as trim on others. Women who were married, or of marriageable age, would likely make sure that their clothing could be adjusted for the stages of pregnancy. For men, they would ensure that their attire would be able to fit comfortably beneath armor (if warriors), and would hold up to the beating that a man gives his clothing.
Most nobles and courtiers would have stewards who would handle the purchase of food on their behalf (or in the case of those at the castles, would dine communally on the monarch’s budget). For their own households, however, it is important to recall that foods could only be grown in certain seasons - so one would likely not get pumpkin in Spring, nor apples in Summer (and with the long seasons in the setting, someone could get quite tired of pears before the Autumn was through!). Eating seasonally and preserving the food for Winter and the early months of Spring would be integral. In general, however, this would all be handled by stewards and cooks for the household, and the bills presented to the master or mistress of the household for the payments due.
Whether hunting dogs, destriers for jousts and battle, or a new hawk, animals were also available to purchase. Pet shops do not exist, however - so dogs are likely bred by a kennelmaster in someone’s House, hawks are likely wild-caught by foresters, and horses… well, we’ll get back to you on that! Cats are generally treated primarily as mousers/ratters, though may occasionally be had as pets.
As far as ornamental animals are concerned, there are pet birds (songbirds), and other possible pets may exist, but these should be treated as uncommon even within noble houses; check with the staff before saying your character has a monkey, a tame leopard, or an elephant!