Such a cute little bundle of colours. He suits his name perfectly.
I like to shop in the 'small' and 'medium' sections for mine but, depending on what kind of toy it is, I might select something from the larger section as well (I'd obviously avoid swings/perch type toys with really big diameters or anything made of hard wood that's meant to be chewed - since I can't imagine it'll get much use.) Gem has never been a fan of ladders, and I've never given one to Panda - but they both enjoy boings. Toy size is also dependant on the size of the cage you want to house him in. The bigger the cage - the more room there is for bigger, more interesting toys to climb around on.
As for food - I was told when I got Gem that foods catering to cockatiels would be suitable to lovebirds. Ive found that the bigger the pellet I give them (they eat cockatiel sized zupreem natural mixed with budgie sized fruit pellets and Gem used to eat the small-ish Hagen cockatiel pellets), the more apt they are to soak their pellets in their water. Where there's a will - there's a way.
I've found nutriberries to be kind of messy - if I feed them by hand, Gem takes off large chunks but drops most of them and if I throw them in a bowl in her cage, they end up on the cage floor. I don't know if they come in different sizes, my bag doesn't say but they're essentially the size of a quarter in spherical format. Personally, I kind of like avicakes better - they're softer and easier for the birds to rip apart.