I haven't used Marketplacepro, but if you are an eBay beginner I can give you some pointers that may be helpful.
The bottom line is a new seller does not need an expensive auction system, they need plenty of hands-on selling experience. If you haven't already, start selling on eBay - you do not need any special software at this stage - just go ahead and sell unwanted items that you have in the house. Aim to get the best price for your goods and provide a fast and friendly service to your buyers. You will learn very quickly after only a few sales.
After you have sold your own unwanted stuff, you will need to look elsewhere for stock. You will soon realise that competition for saleable merchandise is fierce; the wholesalers know this and there are no guarantees of a good deal. You will need to become a specialist in products that genuinely interest you, and research that market until you know it intimately. Then you will be much more able to spot bargains you can resell at a profit.
Another approach that is popular is consignment selling, where you sell other people's items for a commission on the sale price. If you can find a strong local market for this service it could "solve" the stock problem, but you still have the work of selling products and the extra challenge of keeping your consignors (the people you sell for) happy.
If that all sounds like a lot of work, that is because it is. If it were easy, everybody would be doing it and making a fortune - and that just isn't the case.