Q's before purchasing a ruck

[TN FISH]

I am planning on purchasing an rucksack so I can get some experiece in that area. However, looking on ebay I am seeing ruck sacks with and without straps, and also with or without frame...

I was about to purchase one with straps and frame, but wanted to make sure here first before I bought the ruck.

Also can you purchase weights to put in the bag to make it heavy or am I needing to find things I own and pack them up to make it at a desirable weight?

Lastly, I live near a large National Park with LOTS of woods, and also lots of trails. Do you suggest staying on the main roads, and some trails when only traveling with regular shoes?


Thank you.