Regarding making money on the TP for new investors, my best suggestion is to start learning item prices and trends. You already know the general price on a lot of items and don’t really think much about it. Build your own internal watch list (gw2spidy even has an actual watch list) and start learning the values of more items.
Invest in many different items. Not only will you become even more familiar with more items, which means more opportunities, you also greatly reduce risk. It’s also often easier to get things that way too.
If you’re trying to fill some buy order on the cheap for 7500 of an item that only moves 20,000 a day, you’re not going to fill it. People will buy above you. In fact they’ll be more likely to when they see that big 7500 order sitting there and don’t want to wait 8 hours in line to get one large fang or something. Put up a buy for a few stacks perhaps, then go look elsewhere. If you’re trying to find places to invest your money it’s almost always easier buying from 10 different sources than 1-2.
Does every item you bought low end up going way back up? No, but it’s uncommon for it to not work out. Uncommon enough that if you’re investing in many different items and always buying low, I can guarantee you’ll profit.
Don’t be afraid to buy REALLY low either. Items do all sorts of little shifts during the day. Sometimes people just don’t place big investment orders in on them for a couple hours and they drop a lot in price for a short period. I can’t tell you how many times I’ve seen some item with buys of like 1.5s, sell prices of 2s or something…and yet I put in a buy order for 1.1s then wake up the next day and it not only has been filled but the prices are back up for me to sell at 2s to boot. Doesn’t happen with every item, but it happens plenty enough.
Biggest advice of all: Learn what “low” is. If you keep an eye on an item during the day and it didn’t happen to go below a certain point, that doesn’t mean the low part of that point is necessarily a good buy in price. Take a look at what the item did in the past. Put in buys at what you’d really like to buy it for. Worst thing that happens is it doesn’t fill. If you see people investing aggressively and feel like you’re having to fight with them to adjust your buy price to get the item, look elsewhere.
I can tell you every time that I’ve lost substantial amounts of guild wars 2 gold trading, it was because I got greedy and tried to go all in on that “golden ticket” particular item, then it didn’t work out. Can you make big money doing that sometimes? Absolutely. Think about how you’ll feel if it doesn’t work out though. It usually isn’t worth it.