I don't really understand these kind of questions in the abstract. Silver is only of much use if you travel a fair amount on BA. And if you travel a fair amount on BA, you ought to be able to get quite some way towards Silver from your usual travel plans, possibly having to spend a bit more to travel in premium classes. These tips about cheap ways to earn TPs (e.g. via the current sale) are useful to know, but who is really going to get all 600 TPs from CE journeys they wouldn't otherwise undertake to AMS and back?

In other words, to answer the question, one needs to know the OP's normal travel schedule, who pays for the travel, what classes he flies in, how much he can afford, how far in advance he normally books the ticket and so forth. One can then think about how to maximize the TPs from the schedule while remaining in-budget - surely this is where most of the TPs will come from.

I think the closest I've ever come to a TP run is once doing a LGW £59 upgrade to CE primarily for the TPs on a trip I was doing anyway.