Xtra is a great gun for its price of 70-80 dollars, it pretty much comes stock with all the basic things you need. Any upgrades for it would mainly just out of personal taste [regs, hpa, drops (try to stick with things that you can move from gun to gun)]
I don't believe you should spend more than 150 for a package maybe unless its a dragun due to its 20bps but besides that any package for guns such as tippy98(tho i dont like this one personally), any electric spyders, electric fishies under 150 is more than fine. Reason why i mention electrics a lot more than mechs is because its always helpful to have a fast gun in sticky situtions but remember with any electric a electric hopper and very often a new barrel is
nearly required (not always) but this will only cost you 60-70 in total and is well worth it
So to wrap it up
Xtra great
PMI e-Fishies

great, needs barrel and e-hopper
Spyder Electrics same as above
Tippy98 0? not my within my personal taste
Spyder Mechs not bad, needs barrel, e-hopper not really needed,
Pmi Fishies same as above
Dragun T.E.S little more pricey, great bps, not sure if extra price is worth compare to cocker or used electro but still good gun, fast hopper needed
*to reply to that spyder vs tippy*
i cant justify its avg price of 130 and the idea that it can upgrade a lot. True it can stick on flatline and r/t and double trig but spyders/pmi/clones that are electric are slightly more compact, faster, and as upgradable as 98s, they can go high as going full electro fishie o.O so i dunno good gun and all but not worth the 130 for a blowback mech