I'm running a 550 Strength Boost Pet (with just over 500 HP), with a set focused entirely around One Player (with four High Score Charts achieved: Kasuki Lu, Turmaculus, Evil Sloth Clone, and for the moment Tekkitu), and I'm running a Scuzzys Comb as a back-up 10-iconer,

. Mind you, my set has nothing stronger than a 10-iconer, excluding Ghostkerbomb.
Prickly Potion works excellently at the 125 Strength Boost (becoming a 9-iconer against 200 Boost Opponents, 11-iconer against 250, 13-iconer against 300, and going further beyond that). The price will continue to decrease, short of a war, and at r91, restocking one is an option.
I'm not a fan of the Sword of Apocolypse, but given your budget it's fine. Unfortunately, I'm not sure how much credit I would give to the 50% reflectors. Their fragility makes them useless as you max out, limiting their use to DoN battles as well as those against very powerful Opponents whom you will be defeating a very limited number of times.
Ultimately, I aim for consistency. Beyond that, you want to limit the icon types of your weapons so that you become less likely to be blocked. I hate to suggest downgrading, but dual-Scuzzys Combs and dual-Essence of Esophagor look like the best option for lower-end One Player battling.
Ring of the Lost is
the the best way to deal with Dark in One Player. Now, that's not an entirely true statement, but with Ultimate Dark Reflectorb being twice its price, and Ghostkershield being nigh-useless up until you've got around the 550 Defense Boost, it becomes a very true statement. (It's more true in my case, since UDR ends up netting less total icons so long as RotL isn't being partially blocked.)
Slumberberry Potion is also something you want to look at once you have an extended budget. The multiple and chain-freezes are incredibly powerful, and can prolong cases of maxing out.
Also, I should note that I'm assuming you're referring to maxing out (ie, war) and not just DoN missions, as DoN missions are entirely independent of your set.
Buying a U-Bend of Great Justice (1.3-1.4 mil) off of another player is a better option than Kiko Squeeze Toy (again, there is the budget issue). Even so, it's not something that sees much effective use.
Shadow Shield is a relatively cheap full-Light blocker (1.5 mil or so). Illusens Silver Shield is a full-Earth blocker (2.2 mil or so). Clawed Shield (2.2 mil) is arguably better than Flame Reflectozap (3 mil) (or less powerful to a negligible difference, unless you're me and anal about such things).
Which leaves the Physical options: Winged Scarab (which you will steadily outgrow), Yooyuball Keepers Chest Guard (800K), and Yooyuball Player Sling (2.3 mil when I bought mine a few months ago: possibly more now).
75% reflectors are generally better than full-blockers. However, price being and becoming an issue, the full blockers are probably going to be your choice. Dual-duties (Ring of the Lost and Jhudoras Bewitched Ring) are better than 75% reflectors (assuming equal boosts and no blocking). Wind full-blockage and reflection is expensive (at least 8 mil) due to Ghostkersword.
You'll also want to get your Speed to 201 eventually to utilize Heavy Robe of Thievery.
I know I didn't explain many of these very well, but most of them I either own or seriously considered for my own One Player set. It's also getting late and my brain is slowly frying. In order to be "truly" prepared for One Player (again, it comes to maxing out rather than just single battles), it's going to get expensive.