Hello, and welcome to the Forums.
If it is just to look presentable for sale, I would just do basic grooming. The new owners will have their own ideas, so doing elaborate landscaping can be such a waste. I know I'd rather buy a basic garden than one that has been expensively done up in a way I don't like, especially if the landscaping bill is just going to be tacked onto the cost*. Just pull up the weeds and put down more mulch to cover that black plastic and any weed stubble left behind. I would use bark. You can mix bark and pebble mulch together. It will work fine.
* Real estate agents often lobby for improvements when selling, but the agent pay none of the costs while getting ~5% of the sale price. The assumption is that improvements actually lead to higher selling prices, but often they don't.