Just trying to figure out a good rule of thumb, kind of late to the game however am 53 and want to fast track my bullion investing for future goals have other significant investments but want to stay well diversified
Whatever you think you can justify without risking your other assets. For some it will be $20, for others $2000, and for the rare few $20,000 or more. As for 5%-10% of your portfolio, as someone replied above, that is subjective. Keynesians, who never used to advocate PMs, and now saying that. But many Austrians advocate more. I say it should be whatever you are comfortable with. Personally, I make sure I have enough put aside for retirement without selling any PMs and then I put the rest into PMs in some form. That way they are my safety net which I hope I never have to use. For obviously reasons I am not going to give you a dollar amount or a percentage.
What ever you can afford to sit on until the cycle makes the endeavor profitable. Since you're often in the hole as soon as you buy, it could be months, years, or decades before a profit is realized. Hopefully I've got a few decades left to find an appropriate time to exit the PM collection world. Holding something shiny is also more fun than some account sitting in some institution where you can't fondle the goods.
I can't give you a number, but the amount I collect allows me to continue to pursue other investment opportunities. My rule for PMs is that it's purely for emergency and/or extremely long term. My general rule is I don't spend money on PM if I'll need that money in 5-10 years. Everything I buy I consider excess and treat it as such. I hope I never have to touch my PM and also that my other investments pay off.
My process isn't entirely clear. It is essentially DCA (dollar cost averaging) except that I'm very inconsistent about it. I'd like to say I only buy low, but it's actually more of a matter of whether I need to be buying other things or not, and how much cash exposure I think I may need for future expenses so that I should never have to sell. Sometimes I will go a year without getting anything, and other times I'll nibble at the LCS and the online retailers over a period of a few weeks. Right now since summer is coming I have been making smaller nibbles, but I like the price action.
I am going to start with $300 a month and move up from there have about 40 rounds now, since i just started going to get a 10 OZ Bar by this weekend