In addition to what was recommended, I suggest a Brass Range Rod with a T handle & bore guide, a extra cleaning Jag long type), a breech scraper & also a T/C patent breech breech scraper (or you can make one with a .36 cal breech scraper) 2 spare Lyman vent liners, a caliber size bronze bore brush, a short starter..
You can use 2F or 3F in the .54 cal, I used 3F in mine with good accuracy. Used 3F for deer hunting but I was not comfortable with the chamber pressure to shoot it all the time at the range. You can use 3F or 4F for the pan charge. If you decide to use 4F for the pan you can get a brass charger for the pan, normally there are 2 sizes & I suggeswt getting the largest of the two. The small ones clog easily & don't work nearly as well as the larger one. Also if you get 4F just get one can as one pound of 4F lasts forever......
For a vent pick you will find the small hand forged ones from TOW work well. Also you can make them with a piece of gem clip & a dowel or piece of horn as a handle. Or a small piece of SS wire works well & doesn't rust or corrode.
Were it me I would modify the vent right from the get-go, as I have never seen a GPR ignition be good without the vent modified. Have had several tell me theirs was good til they tried a modified vent liner in their rifle & then they found out what good really was. (That is why I suggested 2 spare liners) Wrap the vent liner in a piece of leather & clamp it in a vice, drill & cone the rear with a #2 centerdrill, then slightly cone the front of the liner about half of the screwdriver shot being removed. When ya put the vent liner in just barely snug it & I mean barely. Use a screwdriver that you grind to FIT the slot fully & perfectly & go have some fun at the range.
Best acccuracy I had with a GPR is with one I had with the Lyman Peep sights on it & it would shoot 1" to 1.5" groups at 100 yards. I was shooting 75 grains of 2F Goex, .015 Oxjoke patch, .535 Hornady RB, Lehigh Lube out of a 2 oz punp spray bottle holding it about 3" from the patch. Swabbing between shots, down & back one time with a T shirt patch on a modified jag & 3 squirts of Lehigh on the swabbing patch. (If it is humid out go with 2 squirts of the liquid lube)
Oh, you may as well start looking for a tackle boxes & get one for a range box. I use a large Plano one that has the lid that folds down from the side & has about 5 drawers in the front. The top opens like normal box & that is where I keep the balls, powder, starters & misc stuff. They have a shgooting/cleaning box at WalMart now & then * it is nice. Has a cradle rest that snaps into place on it & has allot of compartments.
Good Luck ! :thumbsup: