By all means practice combos! Make them as long and tricky as you can. Building stamina is very useful. Practice all the 'precursor' moves for the more advanced ones. Butterfly, for example, you can do in split grip and then practice taking the weight off the hooked leg by straightening it gradually (keeping the leg still on the pole and not leaning it out into a full Extended Butterfly until you are confident with your grip). This also leads up to stuff like straight edge and aysha. if you have strong 'precursors' and have used the contact points and set up positions before, it's not too much of a stretch to move on. Watch lots of vids of the advanced moves you want to try, that helps me.
Strengthening - for all of these suggestions, engage the core and be careful of your back:
Aerial and/or from floor lifted choppers (as Charley suggested). Go into a pole pull up, legs straight and keep them locked out and then flip over into chopper. Pretty sure I do it in all of my later vids. Fold it out and do it again, see how many in a row you can get. Also try a chopper, fold it out, still aerial, then swing legs to the other side and chopper, fold it out then switch sides again etc.
Lifted SM (same as chopper - legs straight all the way up and no kicking). Shoulder Mount is GOLD for building core strength, and when it gets easy there are heaps of variations and moves to do with and add on to it and you can do it slower and slower. You can do a SM hold without flipping it up just pulling the legs up into a chopper position or you could do some SM fan leg kicks in both directions and on both hand grip/shoulder sides if you're not ready to flip it over to get used to the hold and to build abs for it. SM dismount is also great to build up strength.
Spider climb (chopper, gemini, pull up, aerial chopper and gemini on weak side, aerial chopper and gemini good side, repeat over and over) is wicked for core strength and it's fun to see how many reps you can get.
Pole pull ups with leg lifts and poses - pull up and tuck legs to chest and straighten legs (toes to floor) repeatedly. Later, lift straightened legs held together as high as you can, lower and repeat. When this is easy take them to either side and back to centre. Try holding chopper/helicopter/fan legs in a pole pull up. Do all of these repeatedly and aerially maybe going into a sit to rest.
When things get easy, just slow them down, hold them longer and make lengthen your lines to make it harder ๐
My aerial pole moves look strong, but on the floor I can barely do a full pushup and situps still burn... (maybe I'm just lazy?) so... I wouldn't be too worried about trying those aerial moves, but you're good for being safe ๐