I think, more so than being realistic, the first thing you do is figure how exactly how much money it will take you to finish the game… Whether it is simply your living expenses so you can work on it full-time, the cost of hiring artists, composers, etc. Then add relevant KS / IndieGogo fees and probably a little extra "just in case something goes wrong" funds. Because you definitely do not want to find yourself in the situation of running a "successful" Kickstarter only to find out you've exhausted your funds and the game is still buggy or unfinished. If you come up with a decent pitch, you may be surprised how many people back it.
Regarding the combat system, you could even set up the more elaborate / expensive combat system as a stretch goal…
Once you know how much money you need and you are prepared (i.e., you have more good screenshots, a good description of your game (esp. mechanics and features that set it apart from every other fantasy RPG out there), , etc. then you may as well go for it. There's no shame in having a failed KS and nothing in their terms that says you can't learn from your mistakes and try it again. Everyone will tell you running a KS is a full-time job though considering all the time you'll devote to updates, answering questions and contacting various gaming sites in the hopes of getting some coverage.
The reality is the vast majority of people who support crowfunding projects just want the game and most people will expect a digitial copy for $15 (or less) since that's been the standard set by most of the big successful KS. Most people aren't going to pledge as much for your game than they did for Wasteland 2, PoE, etc.… (Frankly you should probably offer it for $10 and possibly an early bird tier for even less). Then of course you absolutely should have higher value / limited tiers that offer people the chance to affect the game's development (design a monster / NPC/ quest)… Physical editions are probably not worth the cost unless you get a huge demand for them but there are lots of "creative input" style rewards you could offer people.
From what I've seen so far, I'm potentially interested in supporting your game, but I would expect more info before saying I'd definitely contribute… As I've said, the main question you need to answer is "What will set Lands of Adventure apart from all the other first person, turn-based cRPGs?" What will it do that hasn't been done before or what does it do better? You'd be surprised how many Kickstarters fail to answer this simple, important question.
I wish you luck and I'll keep an eye on this thread.
Edit: I looked up your old Kickstarter page and can tell you one huge thing you did wrong: Do not offer special quests or game features for the higher level tiers… Everyone who pledges at the lowest level should receive a complete copy of the game; if people think they are receiving a "gimped" copy / need to pay micro-transactions to get the whole game, they won't back it. Higher level tiers should be for things like afforementioned creative input, (possibly early alpha / beat access), and possibly digital copies of the soundtrack, digital world map, etc… Also, obviously the pitch video needs to be more attention grabbing / you should tell me in the first 30 seconds why I "need" to play this game as opposed to just getting Might and Magic X.