As a returning collector, I am in more or less your position so this is what I have decided.
1. Decide on a Topic - I have decided to collect Classic US, Commonwealth but I am focused on Queen Victoria for Common Wealth. This is by itself a huge goal (at least for me).
2. Since I had to restart from scratch, I decided to buy off
ebay, I bought a small lot from a dealer but he charged me total CV and being a returnee and unaware of actual market prices I bought for CV.
3. That was the first and last time I buy from a dealer for some time. I am strictly sticking to
ebay and buying the cheaper more easily available stamps at the moment. Once the collection starts getting more complete and the rarer stamps are missing, then it will become more challenging on my pocket.
Keeping this in mind too, I buy only under a few conditions:
1. Firstly, very good deal (compared to CV)
2. Topical Stamps
3. I am able to afford it.
I am staying away from stamps that cost $ 5 and up for a single stamp for the moment.
I also have 2012 Scott for Classic stamps which is my bible when I am on
ebay, to make a price comparison.
As far as bidding goes, i've not done too bad. Sometimes you win , sometimes you dont. I am also not agressive while bidding. I decide an amount I am going to pay and stick to it, if someone beats me, good luck to them :)
In short, if you have a lot of money you can probably buy stamps off higher value in good condition. But like me if you don't then thats going to be tough.