Start with 3 point on one of the skills and 2 on the other one as you can buy the lower skills cheaper starting with 3 saves a lot. Competence and Charisma looks like the key, but the others will be helpful too. In case you have no idea about the value of the goods insight is amazingly helpful. And Luck is directly affecting amount of your daily customers.
When buying goods, offer %70-80 of your estimation or their offering, early on the game use %80 and try not to rise your offer. If they don't accept your offer, they'll most likely say they're not moving at one point if their offer is lower than your estimation it's ok. In case they leave don't worry you'll have lot more customer.
Even if they're on the edge of your estimation try to buy the goods with low condition as you can restore them and sell them with lots of profit.
When you start buying expensive items, don't feel like you must buy them. Ofc buying them with %90 of your estimation will end up great profit. They can be fake items, even if you can sell them with great profit, you may lose lots of reputation. So, use the help of your expert too. When you have 8 or higher competence you don't have to worry about the fake items.
When selling goods, %120-125 of your estimation is good point to start haggling, don't try to sell your goods at the highest price. You don't have much space, so keep buying and selling goods even with to low profit.
Weekly Cost Is Important
Watch your weekly cost and try to save that amount for the day 7 and don't rise your weekly cost too much having staff with 3 stars early in the game can be painful you don't want to waste all your profit to fixed cost. Having an expert and 2 restorers with 1 star is enough until skills are expensive. Even if you don't need it, keeping 30-40k might be helpful as you'll lose some of the goods to the mafia and you might want to buy some "defense".
Buying from auction is great on the early game, join all of them. But if you can't estimate the value you might end up paying %50 more of the item's value, try not go too far with the items which you don't have an estimation if they're in the good condition. And don't forget items sold in the auction can be fake too.
Selling with auction, just don't do that. Trading or buying items with/from your neighbor is also a bad idea.